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Acute Variables: Training Load (Weight and Resistance) Audio

Acute Variables: Training Load (Weight and Resistance)

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This course discusses the optimal load (a.k.a. weight, resistance, or intensity) for strength training, including the optimal weight for the goals of enhancing strength (e.g. 1 repetition maximum strength, or 1-RM strength), strength endurance (e.g. increasing repetitions to failure), hypertrophy (e.g. muscle growth), and power (e.g. increased velocity and athletic performance). Further, optimal weight recommendations are discussed based on training experience, including novice exercisers, experienced exercisers, athletes, children, and elderly exercisers. Additional topics include the effects of training load on blood chemistry, hormones, markers of muscle growth, cardiovascular changes, bone mineral density, body composition (body fat), electromyography, and rate of perceived exertion (RPE).

Some findings from the included systematic research review resulted in counter-intuitive, or at least less conventional recommendations. For example, endurance strength is likely specific to load (and exercise), training with very heavy loads (1-2 RM/set) may be less effective for improving strength, and training load is likely less influential than performing reps-to-failure/set or increasing training volume for increasing muscle mass (hypertrophy). Additionally, the relationship between acute variables is discussed; for example, the "right weight" when planning a strength training block with conventional repetition tempos, for an athlete that has a primary goal of increasing power (e.g. speed or vertical jump height).

Movement professionals (personal trainers, fitness instructors, physical therapists, athletic trainers, massage therapists, chiropractors, occupational therapists, etc.) should consider acute variables essential knowledge for optimal exercise programming, and training load as one of those acute variables. This course is part of our continued effort to optimize “acute variable” recommendations.

Certified Personal Trainer (CPT) Certification

Pre-approved for Continuing Education Credits for:

Acute Variables: Training Frequency and Recovery Between Sessions

Based on the methodologies in the research cited in this review.

 25 or more RM/set (50 % of 1-RM or Less)

*RM = repetition (rep) maximum. The maximum number of reps performed before failure (fatigue).

Position Statement: Optimal Training Load (Weight)

Moderate and heavy loads are likely optimal for most training goals. Moderate and heavy training loads are recommended, and likely the most influential variable for improving strength, with very heavy, light, and very light loads resulting in less or no improvement. Additionally, moderate and heavy loads are likely optimal for improving hypertrophy; however, the load is likely less influential than performing reps-to-failure/set and total training volume. Very light loads with explosive tempos are likely ideal for increasing power (velocity); however, heavier loads result in larger power improvements than lighter loads when comparing strength training with conventional repetition tempos (moderate or slow). Endurance strength is specific to load, and training should aim to increase reps-to-failure/set with a goal/activity-specific load. Last, novice, older, and younger populations should begin training with light or moderate loads, and progress to heavy load training. In summary, cycles of moderate and heavy load training are likely ideal for most training goals. Light and very light loads may only be appropriate for some novice exercisers, while power training with explosive tempos, and/or for some strength endurance goals. Very heavy loads should be reserved for 1 RM practice, and should not be included in regular strength training routines.

 Light loads and very light loads with ballistic tempos (heavy loads during conventional strength training)

Moderate and heavy loads (training volume may be more influential)

 Light and moderate loads, progressing to heavy loads

Load recommendations assume the performance of reps-to-failure/set.

Circuit training, 1 min rest between exercises

Course Summary: Acute Variables: Training Load (Weight and Resistance)

Acute Variables: Load (Weight and Resistance)

Brookbush Institute Acute Variables: Load (Weight and Resistance) Online Course Study Guide

Course Study Guide: Acute Variables: Training Load (Weight and Resistance)

Course Summary Webinar: Training Load (Weight and Resistance)

Light loads and very light loads with ballistic tempos (heavy loads during conventional strength training)

*Load recommendations assume performance of reps-to-failure/set.

The research suggests that load is the most influential acute variable when developing training routines to increase strength. If strength is the goal, it is likely that novice, older, and younger populations should begin training with a moderate load program, and progress to heavy load training. Experienced exercisers should likely use block periodization to cycle through moderate and heavy load blocks. Interestingly, regular training with very heavy loads may be less effective than heavy loads.

Load is an important, but secondary factor when training for hypertrophy, power, and endurance. For example, training with moderate and heavy loads is likely more effective than training with lighter loads for increasing hypertrophy; however, a progressive increase in volume and performing repetitions-to-failure are likely more influential acute variables. Similarly, increasing repetition tempo (explosive rep tempos) is the most influential acute variable for improving power; however, optimal loads (very light loads) are an important factor to ensure that the load is as heavy as can be performed with maximal velocity.

Last, load likely has relatively little influence on improving body composition, bone mineral density, and cardiovascular factors. However, it may be more accurate to say that resistance training has a limited influence on these goals. For example, although heavier loads may have a larger influence on bone mineral density, the research suggests that resistance training does not reliably result in significant increases in bone mineral density.

General Recommendations and Research Summary Statements

Research suggests that load has less influence than volume and reps-to-failure/set on changes in post-exercise concentrations of most hormones and metabolic markers. Further, the large increases in post-exercise concentrations noted after an increase in volume, reps-to-failure/set, or load, tend to return to similar post-exercise concentrations following several weeks of training.

During a resistance training session, faster rep tempos result in larger increases in energy expenditure, heavier loads result in larger increases in muscle oxygenation and anaerobic energy expenditure, and more volume likely results in the largest increases in total energy expenditure and post-exercise serum lactate concentrations (which may result from lighter loads and more reps/set). Further, heavier loads may result in larger increases in systolic blood pressure; however, lighter loads and more "time-under-tension" may result in larger post-exercise decreases in diastolic blood pressure. Additionally, resistance training may not have a significant influence on most cardiovascular measures (resting blood pressure, left ventricular geometry, average and peak heart rate/work rate, VO2 Max, etc.); however, strength endurance training (20-30RM loads) may improve other factors associated with aerobic endurance performance (e.g. alactic power, increased time to exhaustion, and an increase in average and maximal aerobic power).

Increasing load is likely to increase peak and average EMG activity during a set; however, light and moderate loads may result in similar EMG activity during the final reps of sets performed with reps-to-failure. Lighter loads may result in larger increases in EMG activity during power exercises, but only if lighter loads result in faster velocities.

Markers of bone mineral density may improve more following training with moderate or heavier loads; however, based on the available research, resistance training alone may not result in significant improvements.

Heavier loads are likely to result in a higher rate of perceived exertion (RPE). However, performing reps-to-failure/set may result in similar RPE for all loads, especially for the final reps of a set. Additionally, slow tempos may have a larger influence on increasing RPE than load.

Resistance training alone is not ideal for improving body composition but may result in improvements with sufficient training volume and frequency (4x/week or more). Training load likely does not influence body composition improvement; however, if the load does influence results, heavier loads likely result in larger improvements.

Hypertrophy may increase more following moderate to heavy load training when compared to lighter load training; however, training load is likely less influential than performing reps-to-failure/set or increasing training volume. Additionally, different training loads may be recommended to optimize the hypertrophy of different muscles.

Training with moderate loads will result in larger and faster increases in strength than light loads. Training with heavy loads is likely to result in larger increases in strength than moderate loads (especially for compound exercise 1 RM strength). Training with very heavy loads (1-2 RM/set) may be less effective for improving strength, and should likely be considered "max strength practice" and not included in routine training. Last, training with very light loads is likely insufficient to significantly increase strength.

Older individuals and children are likely to exhibit larger or faster increases in strength (and functional outcomes) when comparing training with moderate loads to lighter loads (and performed with reps-to-failure/set). However, moderate and light loads may result in similar improvements when the training volume is similar.

Endurance strength is likely specific to load (and exercise). When endurance strength is measured by reps-to-failure/set with light loads, more reps/set and light loads will result in larger improvements, and heavy loads with fewer reps/set may result in a loss of endurance. However, if the goal is more reps/set with heavy loads, then heavy load training with reps-to-failure/set is likely ideal.

Velocity will likely decrease with increased load, force at peak velocity will increase with increased load, and peak power (P = Work/Time) will occur with light to moderate loads (e.g. 40-70% of 1 RM loads)

When training is performed with conventional strength training rep tempos (moderate to slow tempos), heavy loads are likely to result in larger improvements in power performance (e.g. vertical jump height), and very light loads or training with very slow rep tempos, may result in a decrease in power performance. However, power performance is likely to increase more following a training program with ballistic exercise and very light loads (30% of 1 RM loads or less).

Introduction: Acute Variables: Training Load (Weight and Resistance)

Research Findings: Blood Chemistry and Cardiovascular Changes

Research Findings: Electromyographic Activity (EMG), Bone Mineral Density (Osteoporosis), and Rating of Perceived Exertion (RPE)

Research Findings: Body Composition and Hypertrophy

Research Findings: Strength

Research Findings: Endurance and Power

Research Findings

Quick Summary of Post-exercise Hormone Changes

Increases in post-exercise concentrations with increases in volume, and/or reps-to-failure/set, but load may not have a significant effect.    

Markers of mixed muscle protein synthesis

Markers of myofibrillar muscle protein synthesis

Increases in post-exercise concentrations with lighter loads and higher rep ranges (with and without reps-to-failure/set).

Decreases in post-exercise concentrations with heavier loads (lower rep range), and increases in post-exercise concentrations with lighter loads (higher rep range).

Post-exercise concentrations may not be influenced by changes in load or volume.  

Note, that adaptations to 8-12 weeks of training result in similar post-exercise blood chemistry when comparing various training loads and volumes. Possible exceptions include heavier loads resulting in larger increases in creatine phosphokinase and a decrease in DHEA concentrations, and lighter loads (with higher volume) resulting in higher IGF-1 concentrations.

Lighter loads with higher rep ranges result in significantly larger increases in immediate post-exercise serum concentrations of HGH, IGF-1, testosterone, cortisol, and lactate; with moderate load and rep ranges failing to significantly change concentrations of testosterone, cortisol, and IGF-1.

Glucose concentrations were not significantly affected by load or rep range. Testosterone concentrations increased similarly following both loads but only for men. IGF-1 concentrations increased more following heavy loads (with low reps). HGH concentrations increased more following moderate loads (with moderate reps) for men, but were similar following both loads for women. And, cortisol, lactate, and ammonia concentrations likely increased more following moderate loads, and neither protocol resulted in significant changes in urea or creatinine concentrations.

Comparing Light, Medium, and Heavy Loads:

 Resistance training may not significantly increase free fatty acid concentrations, and although training load likely does not have a significant effect, an increase in exercise volume may increase glucose or leptin concentrations. Additionally, lactate, HGH, and testosterone concentrations may increase more with lighter loads and higher reps; again, exercise volume may be more influential. Last, cortisol concentrations may increase with lighter load/higher volume training, but decrease with heavier load/lower volume training.

Comparing Sets to Failure and Volume with Different Loads:

 This section featured studies in which the higher load protocols also resulted in more training volume (sets x reps x load), which resulted in higher post-exercise serum concentrations of testosterone, sex hormone binding globulin (SHBG), adrenocorticotrophic hormone (ACTH), and HGH (contradicting earlier studies). Further, training-to-failure resulted in significantly higher concentrations of markers of mixed muscle, myofibrillar, and sarcoplasmic muscle protein synthesis, elevated anabolic signaling, and more satellite cell activation. Possible exceptions to the relationship between volume and blood chemistry include IGF-1 increasing more following heavier load training in all studies, sarcoplasmic muscle protein synthesis increasing more with lighter loads and higher rep ranges (with or without reps-to-failure), and most research demonstrating no change in insulin, glucose, luteinizing hormone (LH), or follicle-stimulating hormone (FSH) concentrations.

 Most changes in blood chemistry will adapt to training with various loads, resulting in similar post-exercise concentrations of testosterone, free testosterone, LH, IGF-1, free IGF-1, HGH, and cortisol. Potential exceptions include heavier loads resulting in higher creatine phosphokinase and lower DHEA concentrations, and lower loads (with higher volume) resulting in higher IGF-1 concentrations.

 IGF-1 and IGFBPB-3 may exhibit larger changes in post-exercise serum concentrations when compared to testosterone, HGH, insulin-like growth factor binding protein 1, adrenocorticotropic hormone, glucagon, and cortisol. Further, muscle biopsy for protein synthesis markers has demonstrated that mTor is likely to exhibit larger changes in post-exercise serum concentrations when compared to AKT; however, depending on the time-interval tested post-exercise, heavier loads may result in larger increases in most markers of protein synthesis.

Two studies have compared the change in hormone concentrations following training with moderate and light loads.Fink et al. compared 10 experienced collegiate gymnasts (age: 19.9 ± 1.0 years) randomly assigned to an 8-RM load (and long, 3 min rest between sets) group, or a 20-RM load (and short, 30-sec rest between sets) group. Participants completed a bicep and triceps brachii program (barbell curls, preacher curls, hammer curls, close grip bench press, French press, and dumbbell extensions) for 8 weeks, 3x/week, 3 sets/exercise, reps-to-failure/set, and a moderate (2:0:1) rep tempo. The findings demonstrated that when compared to pre-exercise values, both groups exhibited similar increases in hypertrophy, only the 8-RM load group exhibited significant increases in isometric bicep curl strength, and only the 20-RM group exhibited significant increases in triceps brachii effusion immediately post-exercise. Additionally, results demonstrated that the 20-RM load group exhibited significantly larger increases in post-exercise serum concentrations of human growth hormone (HGH) sampled immediately post-exercise, and a trend to larger increases 15 min, 30 min, and 60 min post-exercise (1). Hakkinen et al. compared 10 highly experienced (bodybuilders, powerlifters, and weight-lifters) male exercisers (age: 29.7 ± 8.0 years) who completed 2 sessions separated by 7 days of squats with 70% or 100% of 1-RM load. The 100% protocol included 20 sets/exercise, 1 rep/set, and a moderate to slow (3-6 sec/rep) rep tempo; the 70% protocol included 10 sets/exercise, 10 reps/set, and an unreported tempo, and both protocols included long (3 min) rest between sets. The findings compared serum (blood) concentrations pre-exercise, and immediately, 1-hour, and 2 hours post-exercise. Only the 70% protocol resulted in significantly increased concentrations immediately post-exercise of serum testosterone, free testosterone, cortisol, and insulin-like growth factor-1 (IGF-1). Testosterone and cortisol concentrations returned to near pre-exercise levels within 1 hour post-exercise, and IGF-1 concentrations returned to near pre-exercise levels within 2 hours post-exercise. Both groups exhibited significant increases in HGH and lactate concentrations; however, the 70% protocol resulted in significantly larger increases. Both groups exhibited near pre-exercise concentrations of lactate within 1 hour post-exercise, and HGH within 2 hours post-exercise (2). These studies suggest that lighter loads with higher rep range result in significantly larger increases in immediate post-exercise serum concentrations of HGH, IGF-1, testosterone, cortisol, and lactate; with moderate load and rep range failing to significantly change concentrations of testosterone, cortisol, and IGF-1.

Three studies were located comparing changes in serum concentrations following moderate and heavy loads. Schwab et al. compared 6 experienced male exercisers (age: 25.2 ± 2.1 years) who completed squats, for 4 sets/session, with 2 different protocols, performed in random order, 1 week apart. Protocol 1 included 90-95% of a 6 RM load with 6 reps/set, and protocol 2 included 60-65% of the weight used for the 90-95% of 6 RM load with 9-10 reps/set. Note that sessions were equated for total weight lifted/session. The findings demonstrated that the heavier load protocol resulted in a larger decrease in plasma volume after a warm-up, after each set of squats, and 10 minutes post-exercise. Both protocols resulted in a similar increase in serum concentrations of testosterone, after a warm-up, and after each set of squats; however, concentrations were similar to pre-exercise values 10 min post-exercise (3). Kraemer et al. (1990) compared 9 recreationally active male exercisers (age: 24.66 ± 4.27 years) who completed 2 sessions in random order separated by 7 days. Both sessions included a full body program (bench press, leg extensions, military press, incline sit-ups, seated rows, lat pulldowns, bicep curls, and leg press). The moderate load program included 10 RM loads, 3 sets/exercise, and short (1 min) rest between sets, and the heavy load program included 5 RM loads, 3-5 sets/exercise, and long (3 min) rest between sets. The findings compared serum (blood) concentrations pre-exercise, and immediately, 5 min, 15 min, 30 min, 1 hour, 1.5 hours, and 2 hours post-exercise. The findings demonstrated that neither protocol resulted in significant changes in glucose concentrations at any time point, lactate concentrations were higher for the 10 RM protocol but the difference between groups was not statistically significant, and increases in testosterone concentrations were similar for both protocols at all time points, HGH concentrations were higher for up to 30 min post-exercise following the 10 RM protocol, and IGF-1 concentrations were higher for up to 5 min post-exercise for the 5 RM protocol (4). Another study by Kraemer et al. (1993) compared 9 recreationally active female exercisers (age: 24.1 ± 4.3 years) who completed 2 sessions in random order separated by 7 days. Both sessions included a full body program (bench press, leg extensions, military press, incline sit-ups, seated rows, lat pulldowns, bicep curls, and leg press). The moderate load program included 10-RM loads, 3 sets/exercise, and short (1 min) rest between sets, and the heavy load program included 5-RM loads, 3-5 sets/exercise, and long (3 min) rest between sets. The findings compared serum (blood) concentrations pre-exercise, mid-exercise, immediately post-exercise, 5 min, 15 min, 30 min, 1 hour, 1.5 hours, and 2 hours post-exercise. HGH increased significantly and similarly for both protocols immediately to 15 min post-exercise, and testosterone and IGF-1 did not increase following either protocol. Further, neither group exhibited significant increases in urea or creatinine concentrations at any time point. Cortisol and lactate increased significantly following both protocols; however, the 10-RM protocol resulted in a trend toward larger increases in cortisol concentrations and was the only group to still exhibit significant increases in lactate 30 min post-exercise. Ammonia concentrations only increased during and immediately following the 10 RM protocol. Finally, both protocols exhibited significant decreases in glucose concentration 1.5-2 hours post-exercise; however, only the 10 RM group exhibited significant increases just 1-hour post-exercise (5). In summary, glucose concentrations were not significantly affected by load or rep range. Testosterone concentrations increased similarly following both loads but only for men. IGF-1 concentrations increased more following heavy loads (with low reps). HGH concentrations increased more following moderate loads (with moderate reps) for men, but were similar following both loads for women. And, cortisol, lactate, and ammonia concentrations likely increased more following moderate loads, and neither protocol resulted in significant changes in urea or creatinine concentrations.

Two studies compared light, medium, and heavy loads, and start to imply direct and inverse relationships between hormone concentrations, load, rep range, and volume. Zafeiridis et al. compared 10 recreationally experienced male exercisers (age: 23 ± 4 years) who completed 4 protocols (control, light, moderate, and heavy) separated by 1 week of rest. The control protocol was a no-exercise session; the light protocol included 60% of 1 RM loads, 15 reps/set, and short (1 min) rest between sets; the moderate protocol included 75% of 1 RM loads, 10 reps/set, and moderate (2 min) rest between sets; and the heavy protocol included 88% of 1 RM load, 5 reps/set, and long (3 min) rest between sets. All participants completed a full body program (bench press, lat pulldowns, squats, and overhead press), 4 sets/exercise, with long (6 min) rest between exercises. The findings compared serum (blood) concentrations pre-exercise, immediately post-exercise, and 30 min post-exercise. All protocols resulted in similar increases in glucose concentrations immediately post-exercise, and a return to pre-exercise values by 30 min post-exercise, but none of the protocols resulted in a significant increase in free fatty acids concentrations at any time point. Additionally, findings demonstrated that leptin concentrations immediately post-exercise decreased significantly following the moderate and heavy protocols, but not following the light protocol. However, all protocols exhibited significant decreases 30 min post-exercise. Further, the amount of work, lactate, cortisol, and HGH concentrations exhibited an inverse relationship to load, with the lighter protocol exhibiting the highest post-exercise lactate concentrations, followed by the moderate, and heavy protocols (6). Smilios et al. compared 11 experienced male exercisers (age: 23 ± 4 years) who completed 8 different protocols with 1 week of rest between each protocol. Two protocols used 52-60% of 1 RM loads with 2 or 4 sets/exercise, 15 reps/set, and short (1 min) rest between sets; 3 protocols used 68-75% of 1 RM load and 2, 4, or 6 sets/exercise, 10 reps/set, and moderate (2 min) rest between sets; and 3 protocols used 80-88% of 1 RM load and 2, 4, or 6 sets/exercise, 5 reps/set, and a long (3 min) rest between sets. All protocols included a full body program (bench press, lat pulldowns, squats, and overhead press), with long (6 min) rest between exercises. The findings compared serum (blood) concentrations pre-exercise, immediately post-exercise, 15 min, and 30 min post-exercise. Post-exercise lactate and HGH concentrations increased with volume increases (reps x sets), exhibiting the highest post-exercise concentrations for the 52-60% of 1 RM load protocols, and higher concentrations for protocols including more sets. Testosterone only significantly increased immediately post-exercise for the 52-60% and 68-75% of 1 RM load protocols with 4 sets/exercise, with all other protocols resulting in statistically similar changes at 15 and 30 min post-exercise. Cortisol significantly increased immediately following the 52-60% and 68-75% of 1 RM load with 2 or 4 sets/exercise protocols and decreased for heavier protocols with more sets (7). These studies suggest that resistance training may not significantly increase free fatty acid concentrations, and although training load likely does not have a significant effect, an increase in exercise volume may increase glucose or leptin concentrations. Additionally, lactate, HGH, and testosterone concentrations may increase more with lighter loads and higher reps; again, exercise volume may be more influential. Last, cortisol concentrations may increase with lighter load/higher volume training, but decrease with heavier load/lower volume training.

Comparing Sets-to-Failure and Different Volumes with Different Loads

Additional studies have compared hormone concentrations and the potential effects of load and performing sets to failure. Raastad et al. compared 9 highly experienced male athletes (7 powerlifters, 1 javelin-thrower, 1 speed skater) (age: 26.9 ± 1.4 years) who completed 3 sessions separated by 1-2 weeks. The 3 sessions included a control (no intervention) protocol, a 70% protocol, and a 100% protocol. The participants performed 70% or 100% of 3 RM load squats and 70% or 100% of 6 RM load knee extensions, for 3 sets/exercise, very long (6 min) rest between sets of squats and front squats, and long (4 min) rest between knee extensions. Note the participants completed the same number of reps for both loads, implying exercise volume was higher for the heavier load protocol (100% of 3-6 RM). The findings on hormones compared serum (blood) concentrations pre-exercise, intra-exercise (30 min into exercise), immediately post-exercise, 15-min, 30-min, 45-min, 60-min, 3 hours, 7 hours, 11 hours, 21 hours, and 33 hours post-exercise. The findings demonstrated that plasma volume and lactate concentrations were higher following the 100% protocol. Testosterone and sex hormone binding globulin (SHBG) concentrations were significantly higher during the 100% protocol, but both protocols resulted in similar testosterone concentrations by 1 hour post-exercise, and SHBG concentrations by 3 hours post-exercise. The 100% protocol resulted in significantly higher concentrations during exercise of adrenocorticotrophic hormone when compared to the 70% protocol, but both protocols resulted in similar post-exercise concentrations. Both protocols resulted in similar decreases in IGF-1 and increases in HGH during exercise, but concentrations near pre-exercise values within 15 min post-exercise. During exercise, the 100% protocol resulted in an increase in cortisol concentration, and the 70% protocol resulted in a decrease in cortisol, but both protocols resulted in similar decreases in cortisol concentrations post-exercise. Last, neither protocol resulted in significant changes in luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin, or glucose concentrations (8). Burd et al. compared 15 experienced male exercisers (age: 21 ± 1 years) with 1 leg randomly assigned to perform 2 or 3, of 3 different exercise protocols. All protocols included knee extensions, 4 sets/exercise, long (3 min) rest between sets, and a moderate (1:0:1) rep tempo. The exercise protocols included 90% of 1-RM load and reps to failure/set, 30% of 1-RM load with reps to failure/set, and 30% of 1-RM load with volume-matched to the heavy protocol (reps not to failure/set). The 90%-to-failure protocol resulted in 5 ± 0.2 reps/set, the 30%-to-failure resulted in 24 ± 1.1 reps/set, and the 30%-not-to-failure resulted in 14 ± 0.5 reps/set, Results demonstrated that 4 hours post-exercise the 30%-to-failure and 90%-to-failure protocols exhibited significantly higher mixed muscle, myofibrillar, and sarcoplasmic muscle protein synthesis values. 24 hours post-exercise all protocols exhibited mixed muscle protein synthesis values similar to pre-exercise values, the 30%-to-failure protocol resulted in elevated myofibrillar muscle protein synthesis, and both the 30%-to-failure and 30%-not-failure protocols resulted in elevated sarcoplasmic muscle protein synthesis. Results demonstrated that all protocols resulted in elevated anabolic signaling, with the 30%-to-failure protocol resulting in more elevated markers of anabolic signaling 4 hours post-exercise, and the 30%-to-failure and 90%-to-failure resulting in more elevated markers 24 hours post-exercise than the 30%-not-to-failure protocol. Results demonstrated that all intervention protocols resulted in increases in satellite cell activation, with the 90%-to-failure and 30%-to-failure resulting in increases in more markers than 30%-not-to-failure. In summary, the higher load protocols also performed more training volume (sets x reps x load), and resulted in higher post-exercise serum concentrations of testosterone, sex hormone binding globulin (SHBG), adrenocorticotrophic hormone (ACTH), and HGH (contradicting earlier studies). Further, training-to-failure resulted in significantly higher concentrations of markers of mixed muscle, myofibrillar, and sarcoplasmic muscle protein synthesis, elevated anabolic signaling, and more satellite cell activation. Possible exceptions to the relationship between volume and blood chemistry include IGF-1 increasing more following heavier load training in all studies, sarcoplasmic muscle protein synthesis increasing more with lighter loads and higher rep ranges (with or without reps-to-failure), and most research demonstrating no change in insulin, glucose, luteinizing hormone (LH), or follicle-stimulating hormone (FSH) concentrations (9).

Additional studies have compared the change in post-exercise hormone concentrations following 8-12 weeks of resistance training with different loads. Morton et al. compared 49 experienced male exercisers (age: 23 ± 1 years) randomly assigned to 30-50% or 75-90% of 1 RM load groups. Participants completed a full body program (leg press, seated rows, bench press, leg curls, front planks, shoulder press, bicep curls, triceps extensions, lat pulldowns, and knee extensions) for 12 weeks, 4x/week, 3 sets/exercise, and reps to failure/set. The 30-50% of 1-RM load group completed 20-25 reps/set and the 75-90% of 1-RM load group completed 8-12 reps/set. The findings demonstrated that both groups exhibited similar improvements in body composition, hypertrophy, and most 10 RM load tests; however, the 75-90% of 1-RM load group exhibited larger increases in bench press 10 RM, and the 30-50% of 1-RM load group completed more volume. Additionally, both groups exhibited similar increases in post-exercise testosterone, free testosterone, LH, IGF-1, free IGF-1, HGH, cortisol, or dehydroepiandrosterone (DHEA) when compared to baseline; however, the 75-90% of 1 RM load group did exhibit a significant decrease in dihydrotestosterone (10). Popov et al. compared 18 physically active male exercisers (age: 21 ± 2 years) randomly assigned to a 50% of 1-RM load group or an 80% of 1-RM load group. All participants completed leg presses for 8 weeks, 3x/week. The 50% of 1 RM load group completed 1 session/week of 4 sets/exercise, and 2 sessions/week of 1 set/exercise, 3 bouts of 50-60 seconds/set, reps to failure/bout, short (0.5 min) rest between bouts, reps performed without locking out joints and continuous tension on muscles, and long (10 min) rest between sets. The 80% of 1 RM load group completed 1 session/week of 7 sets/exercise and 2 sessions/week of 3 sets/exercise, with 6-12 reps to failure/set. Results demonstrated that the 80% of 1 RM load group performed a significantly larger total training load, and exhibited a trend (failed to reach statistical significance) toward larger improvements in strength, and quadriceps and gluteus maximus cross-sectional area (CSA). Additionally, when both groups were assessed for pre- and post-exercise serum concentrations at 2 and 7 weeks, both groups exhibited similar concentrations of lactate and testosterone, the 80% of 1 RM load group exhibited significantly higher concentrations of creatine phosphokinase, and the 50% of 1 RM load group exhibited significantly higher post-exercise serum concentrations of growth hormone, IGF-1, and a larger decrease in the testosterone-to-cortisol ratio at week 7 when compared to week 2 (11). These studies may imply that most changes in blood chemistry will adapt to training with various loads, resulting in similar post-exercise concentrations of testosterone, free testosterone, LH, IGF-1, free IGF-1, HGH, and cortisol. Potential exceptions include heavier loads resulting in higher creatine phosphokinase and lower DHEA concentrations, and lower loads (with higher volume) resulting in higher IGF-1 concentrations.

Two additional studies include methodologies with multiple protocols performed by each participant, by randomly assigning a protocol to each leg. This alters the comparisons that can be made. A study by Holm et al. included two protocols during the same session, resulting in post-exercise serum concentrations resulting from the combination of both programs. Holm et al. compared 11 novice male exercisers (age: 25 ± 1 years) with 1 leg assigned to 70% and the other to 15.5% of 1-RM loads. Participants completed knee extensions for 12 weeks, 3x/week, for 10 sets/exercise. The 15.5% of 1-RM load protocol included 36 reps/set with a slow (5-sec/rep) tempo, and the 70% of 1-RM load group completed 8 reps/set with a moderate (8 reps in 25-sec) tempo. Results demonstrated that following the 12-week program the 70% of 1-RM load leg exhibited significantly larger increases in knee extension 1-RM and isokinetic strength, quadriceps cross-sectional area (CSA), and a decrease in type IIx myosin isoforms. This study also evaluated hormone values pre-exercise, and 5-min, 10-min, 25-min, 1-hour, and 2-hours post-exercise. Comparisons cannot be made between loads due to participants completing both loads during each session; however, testosterone, growth hormone, insulin-like growth factor 1 (IGF-1), insulin-like growth factor binding protein 1, insulin-like growth factor binding protein 3 (IGFBP-3), adrenocorticotropic hormone, glucagon, and cortisol were evaluated. When compared to pre-exercise values, only IGF-1 and IGFBP-3 significantly increased immediately post-exercise, levels of IGF-1 and IGFBP-3 levels returned to pre-exercise values within 10-min post-exercise, and IGFBP-3 levels were significantly increased again 2-hours post-exercise (12). Another study by Holm et al. (2009) compared 20 novice male exercisers (age: 25.6 ± 1.4 years) with 1 leg assigned to 70% of 1 RM load and the other to 15.5% of 1 RM load, with 10 participants completing the exercise in a fasted state, and 10 completing the exercise in a fed state. All participants completed knee extensions during 1 session, 10 sets/exercise, with the 15.5% of 1-RM load protocol including 36 reps/set and a slow (5 sec) rep tempo, and the 70% of 1 RM load group including 8 reps/set with a moderate (8 reps in 25-sec) rep tempo. Intramuscular total collagen protein and myofibrillar protein fractional synthesis rates were measured pre-exercise, and 10-min, 25-min, 1 hour, 1.5 hours, 2 hours, 3 hours, 4 hours, and 5.3 hours post-exercise. The findings demonstrated that compared to pre-exercise values, all interventions resulted in significant and similar intramuscular total collagen protein fractional synthesis. Further, the 15.5% of 1 RM loads group exhibited a trend toward larger increases in the rate of myofibrillar protein fractional synthesis from 10 min to 3 hours post-exercise; however, the 70% of 1 RM protocol exhibited statistically significant increases, that were larger from 4.0 - 5.3 hours post-exercise. Additionally, the fed group likely exhibited larger increases in myofibrillar protein fractional synthesis rate. Last, the 70% of 1 RM load limb exhibited larger increases during the majority of tested time intervals, for most markers of protein synthesis (Rp-s6k-T389, Akt-S473, ERK 1/2-T2022/204, 4E-BP1-T37/46, p38T180/182, AMPk-T172, ACC-S221) (13). Mitchell et al. compared 18 novice male exercisers (age: 21 ± 1 years) with each limb randomly assigned to 2 of 3 protocols: 30% of 1 RM load for 3 sets and reps-to-failure/set, 80% of 1 RM load for 1 set and reps-to-failure/set, or 80% of 1 RM load for 3 sets and reps-to-failure/set. Results demonstrated that all protocols resulted in significant and similar increases in isometric knee extension force, maximal knee extension power output, and knee extension RFD; however, both 80% of 1 RM load protocols resulted in significantly larger increases in knee extension 1 RM strength. Results also demonstrated that all protocols resulted in significant and similar increases in total reps-to-failure and total work during knee extensions with 80% of 1 RM load; however, only the 30% of 1 RM load protocol resulted in significant increases in reps-to-failure during knee extensions with 30% of 1 RM. Results demonstrated that all protocols resulted in significant and similar increases in vastus lateralis type I and type II muscle fiber CSA, and total muscle CSA. Further, muscle biopsy 1-hour after the 1st session was used to determine changes in markers of protein synthesis. None of the protocols increased AKT, all protocols increased mTOR, and only the 80% of 1 RM load protocols increased p70S6K (14). In summary, these studies imply IGF-1 and IGFBPB-3 may exhibit larger changes in post-exercise serum concentrations when compared to testosterone, HGH, insulin-like growth factor binding protein 1, adrenocorticotropic hormone, glucagon, and cortisol. Further, muscle biopsy for protein synthesis markers has demonstrated that mTor is likely to exhibit larger changes in post-exercise serum concentrations when compared to AKT; however, depending on the time-interval tested post-exercise, heavier loads may result in larger increases in most markers of protein synthesis.

Blood Chemistry

During a resistance training session, faster rep tempos result in larger increases in energy expenditure, heavier loads result in larger increases in muscle oxygenation and anaerobic energy expenditure, and more volume likely results in the largest increases in total energy expenditure and post-exercise serum lactate concentrations (which may result from lighter loads and more reps/set). Further, heavier loads may result in larger increases in systolic blood pressure; however, lighter loads and more "time-under-tension" may result in larger post-exercise decreases in diastolic blood pressure. Additionally, resistance training may not have a significant influence on most cardiovascular measures (resting blood pressure, left ventricular geometry, average and peak heart rate/work rate, VO2 Max, etc.); however, strength endurance training (20-30RM loads) may improve other factors associated with aerobic endurance performance (e.g. alactacte power, increased time to exhaustion, and an increase in average and maximal aerobic power).

 During a resistance training session, faster rep tempos result in larger increases in energy expenditure, heavier loads result in larger increases in muscle oxygenation and anaerobic energy expenditure, and more volume likely results in the largest increases in total energy expenditure and post-exercise serum lactate concentrations (which may result from lighter loads and more reps/set). Further, heavier loads may result in larger increases in systolic blood pressure; however, lighter loads and more "time-under-tension" may result in larger post-exercise decreases in diastolic blood pressure.

 The information on caloric expenditure should not be considered alone when attempting to refine training recommendations for body composition improvements. As mentioned above, 2 studies demonstrated that a training program including heavier loads resulted in larger improvements (Fatouros (2005), Tanimoto (2008)).

Cardiovascular Health Following Training:

 Resistance training may have a significant effect on heart rate and vascular function; however, it may not significantly affect most cardiovascular health measures (e.g. resting blood pressure, local common carotid artery distensibility (β-stiffness), left ventricular geometry, etc.).

No Change in Cardiovascular and Cardiorespiratory Factors:

 Resistance training likely does not affect many cardiovascular and cardiorespiratory factors associated with aerobic endurance performance (e.g. RPE, average and peak heart rate/work rate, VO2 Max, etc.), regardless of the load or rep range performed.

 Resistance training may not have a significant influence on most cardiovascular measures (resting blood pressure, left ventricular geometry, average and peak heart rate/work rate, VO2 Max, etc.); however, strength endurance training (20-30RM loads) may improve other factors associated with aerobic endurance performance (e.g. alactacte power, increased time to exhaustion, and an increase in average and maximal aerobic power).

Several studies have compared the effects of training load during resistance training on the cardiovascular system and energy systems. Tanimoto et al. compared 36 novice male exercisers (age: 19.5 ± 0.5 years) randomly assigned to a control (no exercise) group, 55-60% of 1 RM load group, or 80-90% of 1 RM load group. Participants completed a full body program (squats, chest press, lat pulldowns, abdominal "bends", and back extensions) for 13 weeks, 2x/week, 3 sets/exercise, 8 reps/set, reps to failure/set, short (1 min) rest between sets, and moderate (3 min) rest between exercises. The 55-60% of 1-RM load group used a slow (3:0:3) rep tempo with no "relaxation phase", and the 80% of 1 RM load group used a fast (1:0:1) rep tempo and 1-sec "relaxation phase." The findings demonstrated that both intervention groups exhibited significant and similar increases in total 1 RM strength, and both groups exhibited similar increases in squat, chest press, lat pulldown, and abdominal bend 1 RM strength, but the 80-90% of 1 RM load group exhibited the largest increases in back extension 1 RM strength. Additionally, the 80-90% of 1-RM group exhibited significantly larger increases in muscle oxygenation (measured with Near-Infrared Continuous-Wave Spectroscopic Monitor) and blood pressure during exercise, but similar post-exercise oxygenation and serum concentrations of blood lactate (15). Hunter et al. compared 7 experienced male exercisers (age: 24.3 ± 3.8 years) who completed 25% and 65% of 1 RM load protocols separated by 3 days of rest. The 25% of 1 RM load included 1 set/exercise, 8 reps/set, a very slow (5:0:10) rep tempo, and short rest between sets. The 65% of 1 RM load protocol included 2 sets/exercise, 8 reps/set, a fast (1:0:1) rep tempo, and a short (1 min) rest between sets. Both protocols included a full body exercise program; the 25% group completed 8 of the 10 exercises, and the 65% group completed all 10 exercises (leg extension, bench press, bicep curls, leg curls, tricep extensions, rows, bicep curls, military press, upright rows, and squats). The findings demonstrated that the 65% protocol resulted in higher oxygen uptake, heart rate, energy expenditure, and blood serum lactate concentrations during exercise, and higher post-exercise heart rate and energy expenditure 15 minutes post-exercise. Both groups exhibited similar oxygen uptake post-exercise, and neither group exhibited significant changes in respiratory exchange ratio (16). Mazzetti et al. compared 9 experienced male exercisers (age: 20 ± 2.5 years) who completed 4 protocols, including hack squats, with moderate 1.5 min rest between sets, in a randomized, counter-balanced order, over a 6-week period. The protocols included a control (no exercise), a light and moderate protocol that included 60% of 1 RM loads, 4 sets/exercise, 8 reps/set, with a moderate (2:0:2) rep tempo, a light and fast protocol that included 60% of 1 RM loads using the same protocol with the exception of a fast rep tempo (2:0:MaxV), and a moderate and fast protocol that included 80% of 1 RM loads, 6 sets/exercise, 4 reps/set, with a fast rep tempo (2:0:MaxV). The findings demonstrated that all protocols exhibited similar net oxygen consumption; however, the fast protocols exhibited larger increases in energy expenditure. When comparing the two fast tempo groups, the 60% of 1 RM load protocol resulted in higher rates of energy expenditure than the 80% of 1 RM load protocol during exercise and 5, 10, 15, and 30-min post-exercise. Both protocols exhibited similar energy expenditure 45 min post-exercise, and energy expenditure was similar to pre-exercise 60 min post-exercise. Further, 60% of 1 RM load protocol resulted in higher rates of oxidative energy expenditure, lower rates of anaerobic energy expenditure, but more total energy expenditure than the 80% of 1 RM load protocol. Last, the 60% of 1 RM load protocol also exhibited larger increases in serum concentrations of lactate immediately post-exercise, and 15, 30, and 45 min post-exercise, but returned to near pre-exercise levels 60 min post-exercise (17). Hatfield et al. (2006) compared 9 experienced male exercisers (age: 23.9 ± 2.5 years) who completed 4 protocols separated by 72 hours of rest: 60% of 1 RM load with a self-selected rep tempo, 60% of 1 RM load with a very slow rep tempo (10:0:10), 80% of 1 RM load with a self-selected rep tempo, and 80% of a 1 RM load with a very slow rep tempo (10:0:10). Participants completed Smith machine shoulder press and squats, 1 set/exercise, and reps to failure/set. The findings demonstrated that volume was similar for both loads and higher for self-selected tempo protocols than very slow tempo protocols; however, the rate of perceived exertion (RPE) to volume ratio was significantly higher for the very slow rep tempo protocols. Additionally, the self-selected rep tempo protocols did not result in significant changes in post-exercise blood pressure; however, the 80% of 1 RM load with a very slow rep tempo resulted in a significant decrease in post-exercise diastolic blood pressure, and the 60% of 1 RM load with a very slow rep tempo resulted in a significant increase in systolic blood pressure (18). In summary, this research suggests that during a resistance training session, faster rep tempos result in larger increases in energy expenditure, heavier loads result in larger increases in muscle oxygenation and anaerobic energy expenditure, and more volume likely results in the largest increases in total energy expenditure and post-exercise serum lactate concentrations (which may result from lighter loads and more reps/set). Further, heavier loads may result in larger increases in systolic blood pressure; however, lighter loads and more "time-under-tension" may result in larger post-exercise decreases in diastolic blood pressure.

Author's Note: The information on caloric expenditure should not be considered alone when attempting to refine training recommendations for body composition improvements. As mentioned above, 2 studies demonstrated that a training program including heavier loads resulted in larger improvements (Fatouros (2005), Tanimoto (2008)).

One study was located that measured various indicators of cardiovascular health following training with different loads. An RCT by Au et al. compared 46 experienced male exercisers (age: 23 ± 2 years) randomly assigned to 1 of 3 groups. The groups included a control group which maintained their regular physical activity, an 8-12 RM/set group (75-90% of 1-RM loads), and a 20-25 RM/set group (30-50% of 1 RM loads). The two resistance training groups completed a full body program (leg press, rows, bench press, leg curls, front planks, shoulder press, bicep curls, tricep extensions, lat pulldowns, and knee extensions), for 12 weeks, 4x/week, 3 sets/exercise, a combination of single sets and super sets, reps to failure/set, and short (1-min) rest between sets. Findings demonstrated that both groups exhibited similar increases in leg press 1 RM strength; however, the 8-12 RM load group exhibited larger increases in bench press 1 RM strength. Additionally, neither group exhibited a significant change in resting blood pressure, mean arterial pressure, carotid lumen diameter, local common carotid artery distensibility (β-stiffness), and left ventricular geometry; however, both intervention groups exhibited similar decreases in resting heart rate, increases in carotid pulse pressure, and reductions in central arterial stiffness. This study implies that resistance training may have a significant effect on heart rate and vascular function; however, it may not significantly affect most cardiovascular health measures (e.g. resting blood pressure, local common carotid artery distensibility (β-stiffness), left ventricular geometry, etc.) (19).

No Change in Cardiovascular and Cardiorespiratory Factors

Two studies demonstrate that resistance training may have little influence on the cardiovascular and cardiorespiratory factors associated with aerobic endurance performance. Keeler et al. compared 14 novice female exercisers (age: 32.8 ± 8.9 years) randomly assigned to 1 of 2 groups: 55% of 1 RM load with a very slow (5:0:10) rep tempo, or 80% of 1 RM load with a slow (4:0:2) rep tempo. Participants completed a full body program (leg press, leg curls, knee extensions, "anterior lateral pulldowns," bench press, seated rows, bicep curls, and tricep pressdowns) for 10 weeks, 3x/week, 8-12 reps/set, and reps to failure/set. Results demonstrated that when compared to pre-intervention values, the 80% of 1 RM load group exhibited significantly larger increases in 1 RM strength for leg press, leg curls, knee extensions, lat pulldowns, and bench press, as well as total 1 RM strength. However, during a cycle ergometer test, neither group exhibited significant changes in peak rating of perceived exertion, peak heart rate, peak respiratory quotient, peak expired volume per unit time, VO2 max, anaerobic threshold, increases in exercise time, or work rate during a cycle ergometer test (20). Netreba et al. compared 18 physically active males (age: 20± 4 years) randomly assigned to a 50% of 1 RM load (circuit-type training) group, or an 80-85% of 1 RM load (conventional resistance training) group. Participants completed multi-joint lower extremity exercises (including hip extensors, and knee flexors and extensors) on a Power Hummer machine for 8 weeks, 3x/week. The 50% of 1-RM load group completed 3 sets/exercise, 1-4 supersets/circuit, reps performed without locking out joints and continuous tension on muscles, short (0.5 min) rest between sets, and long (10 min) rest between circuits. The 80-85% of 1 RM load group completed 3-7 sets/exercise, 6-10 reps/set, reps to failure/set, and long (10 min) rest between sets. The findings demonstrated that both groups exhibited significant increases in 1 RM strength; however, the 80-85% of 1 RM load group exhibited an average increase of 34%, and the 50% of 1 RM load group exhibited an average increase of 21%. Additionally, the findings demonstrated that neither group exhibited significant improvements in aerobic threshold, anaerobic metabolism threshold, or maximum oxygen consumption during a graded cycle ergometer test; however, both groups exhibited significant and similar increases in maximum alactic power (Wingate test) (21). These studies imply that resistance training likely does not affect many cardiovascular and cardiorespiratory factors associated with aerobic endurance performance (e.g. RPE, average and peak heart rate/work rate, VO2 Max, etc.), regardless of the load or rep range performed.

Additional studies demonstrate that resistance training may not affect most cardiovascular and cardiorespiratory factors associated with aerobic endurance performance; however, resistance training may influence other factors. As mentioned above the study by Netreba et al. demonstrated that active males (age: 20± 4 years) assigned to a 50% of 1 RM load (circuit-type training) group, or an 80-85% of 1 RM load (conventional resistance training) group for 3 weeks, 3x/week, exhibited significant and similar increases in maximum alactic power (Wingate test) (21). An RCT by Rana et al. compared 34 novice female exercisers (age: 21 ± 2.7 years) randomly assigned to 1 of 4 groups: control (no exercise), 6-10 RM load with a moderate (1-2:0:1-2) rep tempo, 6-10 RM load with a very slow (4:0:10) rep tempo, or a 20-30 RM load with a moderate (1-2:0:1-2) rep tempo. Participants completed lower body strengthening (Smith-machine squats, leg press, and knee extensions) for 6 weeks, 2-3x/week, 3 sets/exercise, and reps to failure/set. Results demonstrated that the 6-10 RM load with a moderate rep tempo group exhibited significantly larger increases in leg press and knee extension 1 RM strength; however, none of the groups exhibited statistically significant improvements in vertical jump height. Additionally, a cycle ergometer test demonstrated that the 20-30 RM load group exhibited a significant increase in time to exhaustion, a trend toward increased average peak power, and a trend toward improvements (decreased) in maximal oxygen consumption. The other groups failed to exhibit statistically significant improvements; however, trends were noted that imply more reps/set and moderate rep tempos (when compared to very slow rep tempos) resulted in larger improvements in time to exhaustion and average peak power (22). Last, an RCT by Campos et al. compared 32 novice males (aged: 22.5 ± 5.8 years) randomly assigned to 4 groups: a control group (no exercise), a 3-5 RM load group, a 9-11 RM load group, or a 20-28 RM load group. Participants completed lower body strengthening (leg press, squats, and knee extensions) for 8 weeks, 2-3x/week, volume equated (load × reps × sets), with reps to failure/set. The 3-5 RM load group completed 4 sets/exercise with long (3 min) rest between sets, the 9-11 RM load group completed 3 sets/exercise with a moderate (2 min) rest between sets, and the 20-28 RM load group completed 2 sets/exercise with a short (1 min) rest between sets and exercises. The findings demonstrated that the 3-5 RM load group exhibited the largest increases in squat and leg press 1 RM strength, and the 20-28 RM load group exhibited the smallest increases in 1 RM strength for all exercises. The 20-28 RM load group exhibited the largest increases in endurance strength for all exercises, and the 3-5 RM load group exhibited a significant decrease in leg press endurance. Further, during a cycle ergometer test, none of the groups exhibited a significant change in post-exercise blood lactate levels, VO2 max, pulmonary ventilation, or heart rate reserve percentage. And, only the 20-28 RM load group increased time to exhaustion and maximal aerobic power during the cycle ergometer test (23). Again, these findings suggest resistance training may not have a significant influence on most cardiovascular measures (resting blood pressure, left ventricular geometry, average and peak heart rate/work rate, VO2 Max, etc.); however, strength endurance training (20-30RM loads) may improve other factors associated with aerobic endurance performance (e.g. alactic power, increased time to exhaustion, and an increase in average and maximal aerobic power).

Cardiovascular Changes

Summary: Load and Electromyographic (EMG) Activity

 Increasing load will increase peak and average EMG activity during a set; however, total integrated EMG activity may be higher with lighter loads and more reps/set (more volume). Additionally, light (30-50% of 1-RM) and moderate (70 - 90% of 1RM) loads may result in similar EMG activity during the final reps of sets performed with reps-to-failure.

Comparing Constant and Fluctuating Tension:

 EMG activity will fluctuate significantly more when comparing sets with a pause between reps, and sets that maintain constant tension (no pause between reps). However, this change in EMG likely does not have a significant effect on strength or hypertrophy improvements.

Long-term Effects of Strength Training on EMG Activity: 

Training with heavier loads may increase EMG activity during strength training with heavy loads, increase EMG activity during power exercises with heavy loads, and decrease the reduction in EMG activity that occurs while performing a maximum voluntary isometric contraction (MVIC) for as long as possible (fatigue resistance). Training with lighter loads (and faster rep tempos) may result in larger increases in EMG activity for high-velocity movements with lighter loads.

Several studies have compared the effects of load on electromyographic (EMG) activity during a session. Looney et al. compared 10 experienced male exercisers (23 ± 3 years) who completed a 50% of 1 RM load protocol and 90% of 1 RM load protocol, in random order, during separate sessions with 3 days rest between sessions. Participants completed squats, 1 set/exercise, reps to failure/set, with moderate (2 min) rest between sets. The 50% of 1 RM protocol completed approximately 31 reps/set, and the 90% of 1 RM protocol completed approximately 6 reps/set. The findings demonstrated that both protocols resulted in similar ratings of perceived exertion (RPE), and similar decreases in post-exercise peak isometric force (during squats); however, the 90% of 1 RM load protocol resulted in significantly higher peak vastus lateralis and vastus medialis EMG activity (24). Gonzalez et al. compared 10 experienced male exercisers (age: 22 ± 2.7 years) who completed leg press, for 1 set/load, reps to failure/set, with 70% and 90% of 1-RM in randomized order, with long (15 min) rest between sets. The 70% of 1 RM load resulted in an average of 17.2 ± 4.9 reps/set, and the 90% of 1 RM load resulted in an average of 7.8 ± 3.4 reps/set. The findings demonstrated that the 90% of 1 RM load resulted in higher peak and average quadriceps EMG activity across all reps; however, EMG activity was similar for both loads during the final reps of each set (25). Jenkins et al. compared 9 experienced male and 9 experienced female exercisers (age: 19-29 years) who completed both 30% and 80% of 1 RM loads in two different sessions in randomized order. All participants performed leg extensions, 3 sets/exercise, reps to failure/set, moderate (2 min) rest between sets, and a fast (< 1:0:1) rep tempo. The 30% of 1 RM load protocol averaged 45.6 ± 14.3 reps during the first set, 26.8 ± 8.3 reps during the second set, and 22.2 ± 8.6 reps during the third set; the 80% of 1 RM load protocol averaged 8.9 ± 2.7 reps during the first set, 6.7 ± 1.9 reps during the second set, and 6.2 ± 1.7 reps during the third set. The findings demonstrated that the 30% of 1 RM load protocol resulted in more volume, total work, and concentric time under tension, and exhibited a larger increase in acute post-exercise quadriceps CSA (effusion). The 80% of 1 RM load protocol resulted in greater quadriceps (rectus femoris, vastus lateralis, and vastus medialis) peak and average EMG activity during all 3 sets, and higher EMG activity during the first, middle, and last rep of each set (26). Schoenfeld et al. compared 10 experienced male exercisers (age: 21.3 ± 1.5 years) who completed leg press, 1 set/load, reps to failure/set, and a fast (1:0:1) rep tempo, with both 30% of 1 RM and 75% of 1 RM loads within the same session in a randomized order, separated by 15 minutes of rest. The 30% of 1 RM load resulted in an average of 44.9 ± 13.5 reps/set, and the 75% of 1 RM load resulted in an average of 14.3 ± 5.8 reps/set. The findings demonstrated that the 75% of 1 RM load resulted in higher peak and average EMG activity of the quadriceps (rectus femoris, vastus lateralis, vastus medialis, and biceps femoris) (27). Another study by Schoenfeld et al. compared 12 experienced male exercisers (age: 22.2 ± 2.0 years) performing 50% of 1 RM and 80% of 1 RM loads within the same session, in a randomized order, separated by 15 minutes of rest. The participants completed bench press, 1 set/load, reps to failure/set, with a fast (1:0:1) rep tempo. The 50% of 1 RM protocol resulted in an average of 26.86 ± 4.24 reps/set and the 80% of 1 RM protocol resulted in an average of 10.08 ± 2.19 reps/set. The findings demonstrated that both groups exhibited similar peak EMG activity of the sternal head of the pectoralis major, clavicular head of the pectoralis major, and anterior deltoid; however, the 80% of 1 RM load resulted in higher peak EMG of the triceps brachii. Both loads resulted in similar average EMG activity for the clavicular head of the pectoralis major and anterior deltoid; however, the 80% of 1 RM load resulted in higher average EMG activity of the sternal head of the pectoralis major and triceps brachii. Further, the 80% of 1 RM load resulted in higher matched integrated EMG (the total EMG when matched for reps) for all muscles, and the 50% of 1 RM load exhibited higher total integrated EMG (the total EMG throughout each set) for all muscles (28). These studies suggest that increasing load will increase peak and average EMG activity during a set; however, total integrated EMG activity may be higher with lighter loads and more reps/set (more volume). Additionally, light (30-50% of 1-RM) and moderate (70 - 90% of 1RM) loads may result in similar EMG activity during the final reps of sets performed with reps-to-failure.

Comparing Constant and Fluctuating Tension During a Program

Two studies compare the outcomes of training with different loads, and constant versus fluctuating tension. Tanimoto et al. compared 24 novice male exercisers (age: 19.5 ± 0.6 years) randomly assigned to groups performing 50% of 1 RM loads with a slow (3:0:3:1) rep tempo (and no relaxation during the amortization phase), or groups performing either 50% or 80% of 1 RM loads with a moderate (1:1:1) rep tempo (and 1 second relaxation during the amortization phase). The 50% slow tempo and 80% moderate tempo groups performed rep-to-failure/set. The 50% moderate tempo group was volume (reps/set) matched to the 80% moderate tempo group. All participants completed knee extensions for 12 weeks, 3x/week, 3 sets/exercise, with short (1 min) rest between sets. The findings demonstrated that the groups exhibited significant differences in strength improvements, including the largest improvements exhibited by the 80% of 1 RM load with a fast rep tempo group, significant increases in isometric torque exhibited by the reps-to-failure/set groups, and significant increases in dynamic knee extension torque at various speeds exhibited by the moderate tempo groups. Additionally, the 50% slow rep tempo group exhibited near constant EMG activity, while the other protocols resulted in large fluctuations in EMG activity (likely due to the absence or presence of relaxation during the amortization phase) (29). Another similar study by Tanimoto et al. compared 36 novice male exercisers (age: 19.5 ± 0.5 years) randomly assigned to a control (no exercise) group, 55-60% of 1 RM load group, or 80-90% of 1 RM load group. Participants completed a full body program (squats, chest press, lat pulldowns, abdominal "bends", and back extensions) for 13 weeks, 2x/week, 3 sets/exercise, 8 reps/set, reps to failure/set, short (1 min) rest between sets, and moderate (3 min) rest between exercises. The 55-60% of 1-RM load group used a slow (3:0:3) rep tempo with no "relaxation phase" and the 80% of 1 RM load group used a fast (1:0:1) rep tempo and 1-sec "relaxation phase." The findings demonstrated that both intervention groups exhibited significant and similar increases in total 1 RM strength, and both groups exhibited similar increases in squat, chest press, lat pulldown, and abdominal bend 1 RM strength, but the 80-90% of 1 RM load group exhibited the largest increases in back extension 1 RM strength. Both groups also exhibited similar increases in pectoralis major, triceps brachii, rectus abdominis, latissimus dorsi, quadriceps, and hamstring muscle thickness (measured via ultrasound); however, neither group exhibited significant increases in biceps brachii muscle thickness. Results demonstrated that the 55-60% of 1 RM load group exhibited constant vastus lateralis EMG due to this group not having a "relaxation" phase. In contrast, the 80-90% of 1 RM load group exhibited large fluctuations in vastus lateralis EMG activity (15). These studies imply that EMG activity will fluctuate significantly more when comparing sets with a pause between reps, and sets that maintain constant tension (no pause between reps). However, this change in EMG likely does not have a significant effect on strength or hypertrophy improvements. Note, that these studies report larger strength improvements with heavier loads, and similar hypertrophy improvements with moderate and heavy loads when performing reps-to-failure/set. Because these findings are congruent with other research, and these studies did not directly compare conventional and constant tension tempos (using the same loads), it is not truly possible to assess whether continuous tension is better or worse for improving strength and hypertrophy.

Long-term Effects of Strength Training on EMG Activity

Additional studies compare the effects of a training program on EMG activity during endurance, strength, and power assessments. Netreba et al. compared 18 physically active males (age: 20± 4 years) randomly assigned to a 50% of 1 RM load (circuit-type training) group, or an 80-85% of 1 RM load (conventional resistance training) group. Participants completed multi-joint lower extremity exercises (including hip extensors, and knee flexors and extensors) on a Power Hummer machine for 8 weeks, 3x/week. The 50% of 1-RM load group completed 3 sets/exercise, 1-4 supersets/circuit, reps performed without locking out joints and continuous tension on muscles, short (0.5 min) rest between sets, and long (10 min) rest between circuits. The 80-85% of 1 RM load group completed 3-7 sets/exercise, 6-10 reps/set, reps to failure/set, and long (10 min) rest between sets. The findings demonstrated that both groups exhibited significant increases in 1 RM strength; however, the 80-85% of 1 RM load group exhibited an average increase of 34%, and the 50% of 1 RM load group exhibited an average increase of 21%. Further, only the 80-85% of 1 RM load group exhibited a decrease in fatigue resistance during isometric knee extensions with a 45-second duration (measured as the decrease in quadriceps EMG activity) (21). McBride et al. compared 26 experienced male exercisers (age: 22.3 ± 1.8 years) randomly assigned and strength-matched across groups (strength matched based on 1 RM strength) to 1 of 3 protocols. The protocols included a control group that maintained their usual exercise, a light protocol that performed 30% of 1 RM loads with 5 sets/exercise, and a moderate protocol that performed 80% of 1 RM loads with 4 sets/exercise. Participants completed Smith machine-loaded jump squats for 8 weeks, 2x/week, with long (3 min) rest between sets. The findings demonstrated that both intervention groups exhibited significant and similar increases in squat 1 RM strength when compared to controls. Only the light protocol resulted in a significant increase in peak velocity and peak power during the re-assessment of jump squats at 30%, 55%, and 80% of 1 RM loads. Further, the lighter protocol resulted in larger increases in jump height during the reassessment of jump squats with 30% and 55% of 1 RM loads; although, only the height increase by the lighter protocol with 30% of 1 RM load was statistically significant. Note, that neither group exhibited any change in jump height during jump squats with 80% of 1RM loads. Additionally, when compared to pre-intervention values the 30% of 1 RM group exhibited the only statistically significant increase in vastus lateralis EMG activity during re-assessment. The increase occurred during jump squats with 30% of 1 RM loads and trended toward larger increases than the 80% of 1 RM load group. The 80% of 1 RM group exhibited a trend toward larger improvement during squat jumps with 55% and 80% of 1 RM load, and during reassessment of squat 1 RM strength; however, these trends failed to reach statistical significance (30). These studies imply that 8 weeks of training with heavier loads may increase EMG activity during strength training with heavy loads, increase EMG activity during power exercises with heavy loads, and decrease the reduction in EMG activity that occurs while performing a maximum voluntary isometric contraction (MVIC) for as long as possible (fatigue resistance). Training with lighter loads (and faster rep tempos) may result in larger increases in EMG activity for high-velocity movements with lighter loads.

Electromyographic (EMG) Activity

Studies Demonstrating No Significant Difference:

 Resistance training may not have a significant effect on bone mineral density, regardless of training load, the age of the exerciser (19 - 79 years), supplementation, or the outcome measure used for assessment (e.g. dual x-ray absometry, urinary cross-labs, osteocalcin levels, etc.).

Studies demonstrating Small Differences: 

Markers of bone mineral density may improve more following training with moderate or heavier loads; however, based on the previously cited research, resistance training alone may not result in significant improvements.

Most studies investigating markers of bone mineral density and osteoporosis and the effects of training load imply these outcomes are not influenced by resistance training. Tanimoto et al. compared 36 novice male exercisers (age: 19.5 ± 0.5 years) randomly assigned to a control (no exercise) group, 55-60% of 1 RM load group, or 80-90% of 1 RM load group. Participants completed a full body program (squats, chest press, lat pulldowns, abdominal "bends", and back extensions) for 13 weeks, 2x/week, 3 sets/exercise, 8 reps/set, reps to failure/set, short (1 min) rest between sets, and moderate (3 min) rest between exercises. The 55-60% of 1-RM load group used a slow (3:0:3) rep tempo with no "relaxation phase" and the 80% of 1 RM load group used a fast (1:0:1) rep tempo and 1-sec "relaxation phase." The findings demonstrated that both intervention groups exhibited significant and similar increases in total 1 RM strength, and both groups exhibited similar increases in squat, chest press, lat pulldown, and abdominal bend 1 RM strength, but the 80-90% of 1 RM load group exhibited the largest increases in back extension 1 RM strength. Additionally, When evaluated with dual X-ray absorptiometry, neither group exhibited significant changes in total body mass, fat mass, or bone mineral density (15). Pruitt et al. compared 26 novice female exercisers, 15 of 26 were prescribed hormone replacement therapy (age: 65-79 years), randomly assigned to 1 of 3 groups: a control (no exercise) group; a group performing 40% of 1 RM loads, 3 sets/exercise, 14 reps/set; and a group performing 80% of 1 RM, 3 sets/exercise, and 7-14 reps/set. Note that the 80% of 1 RM group completed 1 set of 14 reps with 40% of 1 RM loads and then completed 2 sets of 7 reps with 80% of 1 RM loads. Participants completed a full body program (bench press, lat pulldowns, military press, bicep curls, knee extensions, knee flexion, hip abduction, hip adduction, leg press, and back extensions) for 12 months, 3x/week. Note that intervention groups were volume-equated. Results demonstrated that both groups exhibited similar increases in 1 RM strength for the exercises performed in the program. Additionally, despite 15 of 26 participants being prescribed hormone replacement therapy, and all participants taking calcium (500mg/day) and vitamin D (200IU/day) supplementation, neither group exhibited significant changes in lumbar spine (L2-4), total hip, femoral neck, and Ward's triangle bone mineral density, nor changes in parathyroid hormone or osteocalcin levels when compared to pre-intervention values (31). Bemben et al. compared 25 novice post-menopausal female exercisers (age: 41-60 years) randomly assigned to a control group (no exercise), 40% of 1 RM load (16 reps/set) group, or 80% of 1 RM load (8 reps/set) group. Exercisers completed a full body program (hip extensions, hip flexions, hip abductions, hip adductions, knee extensions, leg curls, leg press, shoulder press, bicep curls, tricep extensions, seated rows, and lat pulldowns) for 6 months, 3x/week, 1-3 sets/exercise. The findings demonstrated that when compared to preintervention values, both groups exhibited significant and similar increases in post-intervention lat pulldown, seated row, leg curl, hip adduction, and hip extension 1 RM strength; however, only the 80% of 1 RM load group exhibited significant increases in shoulder press, leg press, knee extension, and hip flexion 1 RM strength. Results demonstrated that when compared to pre-intervention, neither group exhibited significant post-intervention changes in bone mineral density (spine, total hip, femoral neck, Ward's triangle, femoral trochanter, and total body), urinary cross-laps (a marker of bone reabsorption), or serum osteocalcin levels (32). These studies imply that resistance training may not have a significant effect on bone mineral density, regardless of training load, the age of the exerciser (19 - 79 years), supplementation, or the outcome measure used for assessment (e.g. dual x-ray absorptiometry, urinary cross-labs, osteocalcin levels, etc.).

Two studies suggest that training load may have some effect on bone mineral density and markers of osteoporosis. Kerr et al. compared 56 novice post-menopausal female exercisers (age: 40-70 years) with one limb randomized to a control (no exercise) and the other limb randomized to an 8 RM or 20 RM load. Participants completed a full body program (bicep curls, wrist curls, reverse wrist curls, triceps extensions, forearm pronation and supinations, leg press, hip abductions, hip adductions, leg curls, hip flexion, and hip extension) for 12 months, 3x/week, 3 sets/exercise, reps to failure/set, and moderate (2-3 min) rest between sets. The findings demonstrated that the 8 RM and 20 RM load limbs exhibited similar increases in the upper body (wrist curl, reverse wrist curl, wrist pronation and supination, bicep curl, and tricep push down) and lower body (hip extension, hip flexion, hip abduction, hip adduction, and leg press) 1 RM strength. The findings also demonstrated that only the 8 RM load limb exhibited increased trochanteric and intertrochanteric bone mineral density, and increased Ward's triangle (center of the femoral neck as per a DEXA machine) bone density. Further, only the 8 RM load increased ultra distal radius bone mineral density, but only the 20 RM load limb increased mid-radius bone mineral density. Last, results demonstrated that neither limb exhibited changes in proximal radius bone mineral density and femoral neck bone mineral density (33). Taaffe et al. compared 36 novice female exercisers (age: 65-79 years) randomly assigned to 1 of 3 groups: a control group (no exercise), a group performing 80% of 1 RM load with 7 reps/set, or a group performing 40% of 1 RM load with 14 reps/set. Participants completed a lower body program (leg press, knee extensions, leg curls) for 12 months, 3x/week, and 3 sets/exercise. Note that the 80% of 1 RM load group completed 1 set with 40% of 1 RM loads with 14 reps/set and then 2 sets with 80% of 1 RM loads with 7 reps/set. Additionally, groups were volume-equated. Results demonstrated that the 40% and 80% of 1 RM load groups exhibited significant and similar increases in post-intervention leg press and leg curl 1 RM strength at 3, 6, 9, and 12 months. However, the 80% of 1 RM load group exhibited a larger increase in knee extension 1 RM strength at 3 months, despite both groups exhibiting similar increases at 6, 9, and 12 months. Results demonstrated that the 80% of 1 RM load group exhibited no changes in post-intervention femoral bone mineral density when compared to pre-intervention. Interestingly, the 40% of 1 RM load group exhibited a significant decrease in post-intervention bone mineral density when compared to pre-intervention (34). These studies imply that markers of bone mineral density may improve more following training with moderate or heavier loads; however, based on the previously cited research, resistance training alone may not result in significant improvements.

Bone Mineral Density

Several studies discussed in this course reported the effects of training load on the rate of perceived exertion. Day et al. compared 19 experienced participants (males age: 24.7 ± 3.8 years, females age: 22.1 ± 2.6 years) who completed 3 different protocols, 2x/each, on separate days, with at least 2 days rest between sessions. The protocols included a heavy load protocol with 90% of 1 RM loads and 4-5 reps/set, a moderate load protocol with 70% of 1 RM loads and 10 reps/set, and a light load protocol with 50% of 1 RM loads and 15 reps/set. All sessions included the same full body exercise program (back squat, bench press, overhead press, bicep curls, and tricep press downs), 1 set/exercise, with moderate (2 min) rest between sets. The findings demonstrated that the rating of perceived exertion increased with load (35). Alegre et al. compared 23 novice female exercisers (age: 21.7 ± 2.7 years) randomly assigned to a control group (no exercise) or a 50/80% of 1 RM load group. Note that the 50/80% of 1 RM load group completed 50% of 1 RM load for one leg and 80% of 1 RM load for the other leg. The leg using 80% of 1 RM load used 50-70% of 1 RM during the initial 3 weeks of the intervention and then increased to 80% of 1 RM during the remaining 7 weeks of the intervention. The 80% of 1 RM load leg used 6-8 reps/set and the 50% of 1 RM load leg used reps/set to match the mechanical work of the 80% of 1 RM load leg. Note that the 50% of 1 RM load leg completed an average of 49-59 reps/session with the 80% of 1 RM load leg completing 36-40 reps/session. Participants completed knee extensions and leg presses for 10 weeks, 3x/week, 3 sets/exercise, with moderate (2 min) rest between sets, and a moderate (2:0:2) rep tempo. Results demonstrated that both legs exhibited significant and similar increases in knee extension isometric, concentric, and eccentric torque at various speeds and angles, and a higher rate of perceived exertion was noted during leg extensions and leg press when training the 80% of 1 RM load leg (36). Fisher et al. compared 7 novice male exercisers (age: 20.6 ± 0.5 years) with each leg assigned to 50% or 80% of 1 RM loads. Participants completed leg extensions for 6 weeks, 1x/week, 3 sets/exercise, reps to failure/set, moderate (2 min) rest between sets, with a slow (3:0:2:1) rep tempo. The 50% of 1 RM load limb averaged 20 ± 4.3 reps/set and the 80% of 1 RM load limb averaged 9.66 ± 1.94 reps/set. Both limbs exhibited similar increases in knee flexion and knee extension isometric strength; however, the 50% of 1 RM load resulted in higher ratings of perceived exertion (RPE) (37). Looney et al. compared 10 experienced male exercisers (23 ± 3 years) who completed a 50% of 1 RM load protocol and a 90% of 1 RM load protocol, in random order, during separate sessions with 3 days rest between sessions. Participants completed squats, 1 set/exercise, reps to failure/set, with moderate (2 min) rest between sets. The 50% of 1 RM protocol completed approximately 31 reps/set, and the 90% of 1 RM protocol completed approximately 6 reps/set. The findings demonstrated that both protocols resulted in similar ratings of perceived exertion (RPE), and similar decreases in post-exercise peak isometric force (during squats) (24). Last, Hatfield et al. (2006) compared 9 experienced male exercisers (age: 23.9 ± 2.5 years) who completed 4 protocols separated by 72 hours of rest: 60% of 1 RM load with a self-selected rep tempo, 60% of 1 RM load with a very slow rep tempo (10:0:10), 80% of 1 RM load with a self-selected rep tempo, and 80% of a 1 RM load with a very slow rep tempo (10:0:10). Participants completed Smith machine shoulder press and squats, 1 set/exercise, and reps to failure/set. The findings demonstrated that volume was similar for both loads, and higher for self-selected tempo protocols than very slow tempo protocols. Additionally, the rate of perceived exertion (RPE) to volume ratio was significantly higher for the very slow rep tempo protocols (18). In summary, these studies imply that heavier loads are likely to result in a higher rate of perceived exertion (RPE). However, performing reps-to-failure/set may result in similar RPE for all loads, especially for the final reps of a set. Additionally, slow tempos may have a larger influence on increasing RPE than load.

Rating of Perceived Exertion (RPE)

Summary: Training Loads and Body Composition

Resistance training alone is not ideal for improving body composition, but may result in improvements with sufficient training volume and frequency (4x/week or more). Training load likely does not influence body composition improvement; however, if the load does influence results heavier loads likely result in larger improvements.

No Change in Body Composition with Light or Moderate Loads: 

Resistance training alone is not ideal for improving body composition, regardless of whether the training load is light or moderate. Note, that most of the studies in this section included programs performed 3x/week.

Similar Improvements in Body Composition with Light, Moderate, and Heavy Loads: 

Resistance training with sufficient volume and frequency (most of these studies included routines performed 4x/week) can result in significant improvements in body composition; however, training load likely does not significantly affect the amount of body composition.

Significant Difference in Body Composition Improvement when Comparing Loads:

 Training load may have a significant influence on improving body composition; however, contrary to popular belief, heavier loads of 80-90% of 1 RM may result in larger improvements than moderate or light loads.

Author's Note: Statistically Significant Changes in Body Fat % are Challenging to Demonstrate

It should be noted that studies investigating the correlation between exercise and changes in body fat percentage are inconsistent. This may be due to numerous factors including the accuracy of body fat measurement techniques (e.g. relatively large margin of error), the relatively small sample sizes used in most exercise science research, and the relatively small change in percentages that occur following long periods of training (e.g. 15% to 13% body fat). Note, a change of 2% body fat is a pride-worthy accomplishment that likely represents a loss of 3 - 5 lbs of fat and a caloric deficit of between 10,000 - 15,000 calories. Unfortunately, the difference between 15% and 13% body fat, with a sample size of 10 participants, may be mathematically insufficient to demonstrate statistically significant changes with an industry standard of "p-value ≤ 0.05".

No Change in Body Composition with Light or Moderate Loads

Most studies comparing training with light and moderate loads demonstrate no change in body composition. An RCT by Vincent et al. compared 62 novice participants (age: 60-83 years) randomly assigned to 1 of 3 groups: control (no exercise), 50% of 1 RM load with 13 reps/set, or 80% of 1 RM load with 8 reps/set. Participants completed a full body program (crunches, leg press, knee extensions, leg curls, calf raise, seated rows, chest press, overhead press, bicep curls, seated dips, leg abduction, leg adduction, and low-back extensions) for 6 months, 3x/week, 1 set/exercise, with moderate (2 min) rest between exercises. The findings demonstrated that when compared to pre-intervention values, both intervention groups exhibited a similar increase in 1 RM strength of the exercises included in the program, low-back extension total isometric strength, and leg press and chest press endurance (number of reps to failure with 60% of 1 RM load). Results also demonstrated that neither group exhibited significant changes in body weight, body fat percentage, or fat-free mass (38). Keeler et al. compared 14 novice female exercisers (age: 32.8 ± 8.9 years) randomly assigned to 1 of 2 groups: 55% of 1 RM load with a very slow (5:0:10) rep tempo, or 80% of 1 RM load with a slow (4:0:2) rep tempo. Participants completed a full body program (leg press, leg curls, knee extensions, "anterior lateral pulldowns," bench press, seated rows, bicep curls, and tricep pressdowns) for 10 weeks, 3x/week, 8-12 reps/set, and reps to failure/set. Results demonstrated that the 80% of 1 RM load group exhibited significantly larger increases in 1 RM strength for leg press, leg curls, knee extensions, lat pulldowns, and bench press, as well as total 1 RM strength. However, neither group exhibited significant changes in post-intervention body weight, body fat percentage, fat weight mass, lean weight percentage, lean weight mass, or body mass index (20). An RCT by Schuenke et al. compared 34 novice female exercisers (age: 21.1 ± 2.7 years) randomly assigned to 1 of 4 groups including a control (no exercise), a moderate load group performing 80-85% of 1 RM load, 6-10 RM/set with a moderate (1-2:0:1-2) rep tempo, a light load group performing 40-60 % of 1-RM load, 20-30 RM/set with a moderate (1-2:0:1-2) rep tempo, and a light load and very slow tempo group performing 40-60% of 1-RM load, 6-10 RM/set with a very slow (4:0:10) rep tempo. All intervention groups completed lower body strengthening (leg press, squats, and knee extensions) for 6 weeks, 2-3x/week, 3 sets/exercise, reps to failure/set, and moderate (2 min) rest between sets and exercises. Results demonstrated that compared to pre-intervention values, none of the groups exhibited significant changes in body mass, body fat percentage, fat mass, and fat-free mass (39). Harris et al. compared 51 experienced (Division-1 Football) male exercisers (age: 19.4 ± 0.4 years) randomly assigned to 1 of 3 groups: 80-85% or 1 RM loads, 30% of 1 RM loads, or a combination of 80-85% and 30% of 1 RM loads. Participants completed a 4-week introductory program prior to their random assignment. Once assigned to their protocol, participants completed a full body program (squats, bench press, push press, crunches, midthigh pulls, stiff-legged deadlifts, and bent over rows) for 9 weeks, 4x/week, 5 sets/exercise, with 5 reps/set. Note, that there were slight variations in exercise selection between groups, including the 30% and combination groups performing dumbbell squats, and the 80-85% and combination groups performing parallel squats. The findings demonstrated that when compared to pre-intervention values, increases in 1 RM strength were exercise selection specific, including the 80-85% and combination load groups exhibiting significant increases in parallel squat 1 RM strength, and similar increases in some exercises performed by all groups including the quarter squat and mid-thigh pull 1 RM strength. However, the results also demonstrated that none of the groups exhibited a significant change in body mass or body fat percentage (40). These studies likely imply that resistance training alone is not ideal for improving body composition, regardless of whether the training load is light or moderate. Note, that most of the studies in this section included programs performed 3x/week.

Similar Improvements in Body Composition with Light, Moderate, and Heavy Loads

Additional studies demonstrate that resistance training results in significant improvements in body composition, but imply that training loads do not have a significant influence on the amount of improvement. An RCT by Au et al. compared 46 experienced male exercisers (age: 23 ± 2 years) randomly assigned to 1 of 3 groups. The groups included a control group which maintained their regular physical activity, an 8-12 RM/set group (75-90% of 1-RM loads), and a 20-25 RM/set group (30-50% of 1 RM loads). The two resistance training groups completed a full body program (leg press, rows, bench press, leg curls, front planks, shoulder press, bicep curls, tricep extensions, lat pulldowns, and knee extensions), for 12 weeks, 4x/week, 3 sets/exercise, a combination of single sets and super sets, reps to failure/set, and short (1-min) rest between sets. Note that groups were not equated for volume. Findings demonstrated that both groups exhibited similar increases in leg press 1 RM; however, the 8-12 RM load group exhibited larger increases in bench press 1 RM strength. Further, both experimental groups exhibited similar increases in fat-free mass (19). Morton et al. compared 49 experienced male exercisers (age: 23 ± 1 years) randomly assigned to 30-50% or 75-90% of 1 RM load groups. Participants completed a full body program (leg press, seated rows, bench press, leg curls, front planks, shoulder press, bicep curls, triceps extensions, lat pulldowns, and knee extensions) for 12 weeks, 4x/week, 3 sets/exercise. The 30-50% of 1-RM load group completed 20-25 reps-to-failure/set and the 75-90% of 1-RM load group completed 8-12 reps-to-failure/set. The findings demonstrated that the 30-50% of 1-RM load group completed a larger volume of exercise, and despite both groups exhibiting similar improvements on most 10 RM load tests, the 75-90% of 1-RM load group exhibited significantly larger increases for bench press 10 RM strength. Additionally, both groups exhibited similar body composition and significant and similar decreases in total fat mass, bone-free mass, and increases in appendicular and leg lean mass (hypertrophy) (10). An RCT by Rana et al. compared 34 novice female exercisers (age: 21 ± 2.7 years) randomly assigned to 1 of 4 groups: control (no exercise), 6-10 RM load with a moderate (1-2:0:1-2) rep tempo, 6-10 RM load with a very slow (4:0:10) rep tempo, or a 20-30 RM load with a moderate (1-2:0:1-2) rep tempo. Participants completed lower body strengthening (Smith-machine squats, leg press, and knee extensions) for 6 weeks, 2-3x/week, 3 sets/exercise, and reps to failure/set. Results demonstrated that the 6-10 RM load with a moderate rep tempo group exhibited significantly larger increases in leg press and knee extension 1 RM strength, and was the only group to exhibit increases large enough to reach statistical significance when compared to the control group. Additionally, none of the groups exhibited statistically significant changes in body weight; however, all intervention groups exhibited significant and similar decreases in body fat percentage and fat mass, as well as significant and similar increases in fat-free mass (22). Kraemer et al. compared 85 novice female exercisers (age: 23.1 ± 3.5 years) randomly assigned to 1 of 5 groups: control (no exercise); total body with 3-8 RM/set or 8-12 RM/set, and upper body with 3-8 RM/set or 8-12 RM/set. Note that the 3-8 RM load groups performed a moderate (2 min) rest between sets, and the 8-12 RM load group performed short to moderate (0.5-1.5 min) rest between sets. Each group performed a different program. Participants in the total body with 8-12 RM load group completed a full body program (squats, knee extensions, leg curls, dumbbell incline press, chest flyes, lat pulldowns, upright rows, dumbbell rows, and rotational crunches); the total body with 3-8 RM load group completed a full body program (dumbbell clean and press, leg curls, dumbbell incline bench press, lat pulldowns, squats, incline sit-ups, upright rows, dumbbell rows); the upper body with 8-12 RM load group completed an upper body program (bench press, seated row, dumbbell shoulder press, lat pulldowns, bicep curls, tricep press downs, rotational crunches, and back extensions); and, the upper body with 3-8 RM load group completed an upper body program (bench press, seated rows, dumbbell bench press, lat pulldowns, bicep curls, tricep press downs, incline sit-ups, and back extensions). All participants performed these programs for 24 weeks, 3x/week, with aerobic exercise performed 3x/week, 25-35 min/session, with 70-85% of max-HR. The findings demonstrated that when compared to pre-intervention values, all groups exhibited similar increases in bench press 1 RM strength, and the total body groups exhibited similar and significant increases in squat 1 RM strength and jump squat height. Only the total body with 3-8 RM load group exhibited significant increases in post-intervention body mass (and BMI), only the upper body with 3-8 RM group failed to exhibit any increase in fat-free mass, and none of the groups exhibited a significant change in body fat percentage (41). These studies suggest that resistance training with sufficient volume and frequency (most of these studies included routines performed 4x/week) can result in significant improvements in body composition; however, training load likely does not significantly affect the amount of body composition.

Significant Difference in Body Composition Improvement When Comparing Loads

Two studies demonstrate a significant difference in body composition changes when comparing training with different loads. Fatouros et al. compared 50 novice male exercisers (age range: 65-78 years) randomly assigned to 1 of 4 groups: control (intervention not reported), 45-50% of 1 RM with a moderate (2 min) rest between sets, 60-65% of 1 RM with a long (4 min) rest between sets, or 80-85% of 1 RM with a very long (6 min) rest between sets. Participants completed a full-body program (chest press, knee extensions, shoulder press, leg curls, lat pulldowns, leg press, bicep curls, tricep extensions, crunches, and "lower back exercises") for 6-months, with 2-3 sets/exercise. Results demonstrated that when compared to pre-intervention values, the 80-85% of 1 RM load group exhibited the largest increases in trunk and leg 1 RM strength, followed by the 60-65% of 1 RM load groups, and the least improvement was exhibited by the 45-50% of 1 RM load group. Further, all intervention groups exhibited similar decreases in body mass, only the 60-65% and 80-85% of 1 RM load groups exhibited a decrease in skinfold values, and only the 80-85% of 1 RM load group exhibited a decrease in waist-to-hip ratio (42). Tanimoto et al. compared 36 novice male exercisers (age: 19.5 ± 0.5 years) randomly assigned to a control (no exercise) group, 55-60% of 1 RM load group, or 80-90% of 1 RM load group. Participants completed a full body program (squats, chest press, lat pulldowns, abdominal "bends", and back extensions) for 13 weeks, 2x/week, 3 sets/exercise, 8 reps/set, reps to failure/set, short (1 min) rest between sets, and a moderate (3 min) rest between exercises. The 55-60% of 1-RM load group used a slow (3:0:3) rep tempo with no "relaxation phase" and the 80% of 1 RM load group used a fast (1:0:1) rep tempo and 1-sec "relaxation phase." The findings demonstrated that both intervention groups exhibited significant and similar increases in total 1 RM strength, and both groups exhibited similar increases in squat, chest press, lat pulldown, and abdominal bend 1 RM strength, but the 80-90% of 1 RM load group exhibited larger increases in back extension 1 RM strength. Both groups also exhibited similar increases in pectoralis major, triceps brachii, rectus abdominis, latissimus dorsi, quadriceps, and hamstring muscle thickness (measured via ultrasound); however, neither group exhibited significant increases in biceps brachii muscle thickness. Additionally, the findings demonstrated that the 80-90% of 1 RM load group exhibited significantly larger decreases in total subcutaneous fat (80-90% of 1 RM load group: average decrease of 10.2 ± 9.4%, 55-60% of 1 RM load group: mean decrease of 2.1 ± 1.22%); as well as, the only statistically significant decrease at a single site (posterior upper arm). When evaluated with dual x-ray absorptiometry both intervention groups exhibited significant and similar increases in muscle mass, the 80-90% of 1-RM group exhibited a significantly larger decrease in body fat percentage, and neither group exhibited significant changes in total body mass, fat mass, or bone mineral density (15). These studies demonstrate that training load may have a significant influence on improving body composition; however, contrary to popular belief, heavier loads of 80-90% of 1 RM may result in larger improvements than moderate or light loads.

Body Composition

Hypertrophy: Similar Improvements with Different Loads

Hypertrophy: Trends Toward Differences and Differences Between Muscle Groups

Hypertrophy: Differences in Hypertrophy with Different Loads

Hypertrophy

Strength: Comparing Light and Moderate Loads

Strength: Comparing Moderate and Heavy Loads

Strength: Training Loads for Older and Adolescent Populations

Strength: Comparing Extremities

Strength: Comparing the Effects of Load and Tempo

Strength

Endurance Following Training with Different Loads

Author's Note: In this course, "endurance" refers to "strength endurance" and the ability to lift a submaximal load for multiple repetitions. The limit of strength endurance is a combination of muscle strength and anaerobic capacity. This is distinct from aerobic endurance, which is generally limited by the capacity of the cardiorespiratory, and/or cardiovascular system.

 Some research suggests that similar improvements in endurance strength may result from training with light and moderate loads; however, the majority of research demonstrates statistically significant differences.

Lighter Load and Higher Repetitions Better For Endurance: 

A heavier load is likely superior for improving 1 RM strength; however, a lighter load with more reps/set is likely superior for improving endurance strength (reps to failure with 50% or 60% of 1-RM load, or a decrease in relative torque throughout 50 reps).

 Training with heavy loads and fewer reps/set (3-8 RM/set) is likely inferior for improving endurance strength when compared to training with lighter loads and more reps/set (9+ RM/set). Further, some research suggests training with heavy loads may result in a decrease in endurance strength.

 If an increase in endurance strength is tested with light loads then performing reps-to-failure/set with lighter loads will result in larger improvements; however, if endurance strength is tested with significantly heavier loads, then training with heavier loads will result in larger improvements.

 Endurance strength may be exercise-specific, and if strength endurance is the goal of training, endurance training should precede maximal strength training within a session.

Two studies were located that demonstrated improvements in strength endurance were similar with light and moderate loads. An RCT by Vincent et al. compared 62 novice participants (age: 60-83 years) randomly assigned to 1 of 3 groups: control (no exercise), 50% of 1 RM load with 13 reps/set, or 80% of 1 RM load with 8 reps/set. Participants completed a full body program (crunches, leg press, knee extensions, leg curls, calf raises, seated rows, chest press, overhead press, bicep curls, seated dips, leg abductions, leg adductions, and low-back extensions) for 6 months, 3x/week, 1 set/exercise, with moderate (2 min) rest between exercises. The findings demonstrated that when compared to pre-intervention values, both intervention groups exhibited similar improvements in 1 RM strength of the exercises included in the program, low-back extension isometric strength, leg press, and chest press endurance (number of reps to failure with 60% of 1 RM load), and the stair climb test (time to ascend 23 steps) (38). An RCT by Rana et al. compared 34 novice female exercisers (age: 21 ± 2.7 years) randomly assigned to 1 of 4 groups: control (no exercise), 6-10 RM load with a moderate (1-2:0:1-2) rep tempo, 6-10 RM load with a very slow (4:0:10) rep tempo, or a 20-30 RM load group with a moderate (1-2:0:1-2) rep tempo. Participants completed lower body strengthening (Smith-machine squats, leg press, and knee extensions) for 6 weeks, 2-3x/week, 3 sets/exercise, and reps to failure/set. Results demonstrated that the 6-10 RM load with a moderate rep tempo group exhibited significantly larger increases in leg press and knee extension 1 RM strength, and was the only group to exhibit increases large enough to reach statistical significance when compared to the control group. All intervention groups exhibited statistically similar increases in squat, leg press, and knee extension endurance (number of reps to failure with 60% of 1-RM); however, the 20-30 RM load with moderate rep tempo group exhibited a trend toward larger improvements (22). These studies may suggest that similar improvements in strength endurance may result from light and moderate loads; however, the Rana et al. (2008) study exhibited a trend and the majority of research demonstrates statistically significant differences.

Lighter Load and Higher Repetitions Better For Endurance

The majority of the research assessing strength endurance demonstrates statistically significant differences when comparing light load training (higher rep/set) to heavy load training (lower rep/set). An RCT by Faigenbaum et al. compared 43 (11 girls and 33 boys) young novice exercisers (age: 5.2 - 11.8 years), randomly assigned to a control group (no exercise), a 6-8 RM load group, or a 13-15 RM load group. Participants completed a full-body program (leg extensions, leg press, leg curls, hip abduction, pullovers, chest press, rows, abdominal flexion, lat pulldowns, abdominal curls, and low back extensions) for 8 weeks, 2x/week, 1 set/exercise, with reps to failure/set. Results demonstrated that only the 13-15 RM load group reached statistically significant increases in chest press 1 RM strength and endurance strength; however, the differences between the 13-15 RM load and 6-8 RM load groups were not statistically significant. Additionally, the 13-15 RM load group exhibited the largest increases in knee extension strength endurance; however, the 6-8 RM load group also exhibited statistically significant increases (67). Masuda et al. compared 12 novice male exercisers (age: 28.5 ± 4.0 years) assigned to high-volume or heavy-load groups while performing concentric knee extensions for 8 weeks, 2x/week. The high volume protocol included 80-40% of 1 RM load (load decreased with successive sets), 9 sets/exercise, reps-to-failure/set, and short to long (0.5-3 min) rest between sets. The heavy load protocol included 90% of 1 RM loads, 5 sets/exercise, reps-to-failure/set, and long (3 min) rest between sets. The findings demonstrated that the heavy load group exhibited a trend toward larger improvements in 1-RM strength, and only the high volume group exhibited a significant improvement in average strength endurance (measured via the decrease in relative torque throughout 50 reps of knee extensions at 180°/sec) (47). Schoenfeld et al. compared 18 experienced male exercisers (age: 18-35 years) randomly assigned to a 30-50% of 1 RM load group or 70-80% of 1 RM load group. All participants completed a full body program (bench press, military press, lat pulldowns, seated rows, squats, leg press, and leg extensions) for 8 weeks, 3x/week, 3 sets/exercise, reps to failure/set, a moderate (1.5 min) rest between sets, and a moderate (2:0:1) rep tempo. The 30-50% of 1 RM load group completed 25-35 reps/set and the 70-80% of 1 RM load group completed 8-12 reps/set. Results demonstrated that the 70-80% of 1 RM load group exhibited larger increases in squat 1 RM strength, and a trend toward larger increases in 1 RM bench press strength; however, the 30-50% of 1 RM load group exhibited larger increases in upper body endurance (bench press reps to failure with 50% of 1-RM load). Note, that lower body endurance was not tested (45). Van Roie et al. compared 56 novice participants (age: ≥ 60 years) randomly assigned to 1 of 3 groups: a moderate group performing 80% of 1 RM loads with 10-15 reps/set and 2 sets/exercise; a very light/1-set group performing 20% of 1 RM loads with 80-100 reps/set and 1 set/exercise; and a light/very light group performing a 20% of 1 RM load and 60 reps/set for 1 set/exercise followed by 40% of 1 RM load for 10-20 reps/set and 1 set/exercise. Participants completed leg press and knee extensions for 12 weeks, 3x/week, reps to failure/set, with moderate (2 min) rest between exercises, and a slow (3:0:2) rep tempo. The findings demonstrated that compared to pre-intervention values, the groups performing 2 sets/exercise (moderate group and light and very light group) exhibited significant and similar increases in leg press and leg extension 1 RM strength, the moderate group exhibited a trend toward larger increases in leg press 1 RM strength, and the very light 1-set group did not exhibit an increase in 1 RM strength. Results also demonstrated that the light 1-set group, and light and very light group exhibited significant and similar increases in knee extension endurance (number of reps to failure with 60% of 1 RM load), although differences between these groups and the moderate group were not statistically significant. Additionally, only the moderate group exhibited a significant improvement in 6 min walk distance and gait speed tests, only the moderate group and light and very light groups exhibited an improvement on the 30-second sit-to-stand test, and all groups exhibited similar improvements on the 5 reps in the chair sit-to-stand test, and none of the groups exhibited improvement on the timed up-and-go test (50). In summary, these studies imply that a heavier load is likely superior for improving 1 RM strength; however, a lighter load with more reps/set is likely superior for improving strength endurance (reps to failure with 50% or 60% of 1-RM load, or a decrease in relative torque throughout 50 reps).

Two additional studies suggest that lighter loads and higher reps/set are superior for strength endurance, and demonstrate that heavy loads and fewer reps/set may result in worse endurance. Anderson et al. compared 43 novice male exercisers (age: 20.65 ± 1.79 years) randomly assigned to 1 of 3 groups: a 6-8 RM load group, a 30-40 RM load group, or a 100-150 RM load group. Participants completed the bench press exercise for 9 weeks, 3x/week, reps to failure/set, moderate (2 min) rest between sets, and a fast (40 reps/minute) rep tempo. The number of sets/exercise differed for each group; the 6-8 RM load group completed 3 sets/exercise, the 30-40 RM load group completed 2 sets/exercise, and the 100-150 RM load group completed 1 set/exercise. Note, that all groups completed equal volume. The findings demonstrated that bench press 1 RM strength increased by an average of 20.22% in the 6-8 RM load group, 8.22% in the 30-40 RM load group, and 4.92% in the 100-150 RM load group. Relative endurance (as many reps as possible with 40% of 1 RM at a rate of 40 reps/min) decreased by an average of 6.99% in the 6-8 RM load group, increased by 22.45% in the 30-40 RM load group, and increased by 28.45% in the 100-150 RM load group. And, absolute endurance (as many reps as possible with 27.23 kg at a rate of 40 reps/min) increased by 41.30% in the 100-150 RM load group, 39.23% in the 30-40 RM load group, and 23.56% in the 6-8 RM load group (54). An RCT by Campos et al. compared 32 novice males (aged: 22.5 ± 5.8 years) randomly assigned to 4 groups: a control group (no exercise), a 3-5 RM load group, a 9-11 RM load group, or a 20-28 RM load group. Participants completed lower body strengthening (leg press, squats, and knee extensions) for 8 weeks, 2-3x/week, volume equated (load × reps × sets), with reps to failure/set. The 3-5 RM load group completed 4 sets/exercise with long (3 min) rest between sets, the 9-11 RM load group completed 3 sets/exercise with a moderate (2 min) rest between sets, and the 20-28 RM load group completed 2 sets/exercise with a short (1 min) rest between sets and exercises. Outcome measures included 1 RM strength and endurance (number of reps with 60% of 1 RM) for squats, leg press, and knee extensions. The results demonstrated that the 3-5 RM load group exhibited the largest increases in squat and leg press 1 RM strength, followed by the 9-11 RM group, both the 3-5 RM and 9-11 RM groups exhibited similar increases in knee extension 1 RM strength, and the 20-28 RM load group exhibited the smallest increases in 1 RM strength for all exercises. The 20-28 RM load group exhibited the largest increases in strength endurance for all exercises, only the 20-28 RM load group exhibited a significant increase in knee extension endurance, all groups exhibited significant increases in squat endurance, and the 3-5 RM load group exhibited a significant decrease in leg press endurance (22). These studies imply that training with heavy loads and fewer reps/set (3-8 RM/set) is likely inferior for improving strength endurance when compared to training with lighter loads and more reps/set (9+ RM/set). Further, this research suggests training with heavy loads may result in a decrease in strength endurance.

Additional studies suggest that improving strength endurance may be specific to training load. Mitchell et al. compared 18 novice male exercisers (age: 21 ± 1 years) with each limb randomly assigned to 2 of 3 protocols for 10 weeks: 30% of 1 RM load for 3 sets and reps to failure/set, 80% of 1 RM load for 1 set and reps to failure/set, or 80% of 1 RM load for 3 sets and reps to failure/set. The findings demonstrated that all protocols resulted in significant increases in isometric knee extension strength; however, both 80% of 1 RM load protocols resulted in significantly larger increases in knee extension 1 RM strength, and only the 30% of 1 RM load protocol resulted in significant increases in endurance at 30% of 1 RM load (14). De Vos et al. compared 112 novice participants (age: 69 ± 6 years) randomly assigned to 1 of 4 groups: a control (no exercise) group, or groups performing 20%, 50%, or 80% of 1 RM loads. Participants completed a full body program with pneumatic machines (leg presses, seated chest press, knee extensions, rows, and leg curls) for 8-12 weeks, 2x/week, 2-3 sets/exercise, short (10-15 sec) rest between reps, and a moderate (3:0:MaxV) rep tempo. Note that participants "alternated exercises after each set," but the study did not provide specifics. Results demonstrated that when compared to pre-intervention values, all intervention groups exhibited similar average increases in peak torque and peak power, the 80% of 1RM load group exhibited the largest increase in 1 RM strength for most exercises, followed by the 50% group, and then the 20% group. Interestingly, results demonstrated that the 80% of 1 RM load group exhibited the largest increases in endurance, and the 50% and 20% groups exhibited less improvement in strength endurance. This is likely due to endurance being assessed with as many reps as possible with 90% of pre-intervention 1 RM load (62). Stone et al. compared 50 novice female exercisers (age: 23.1 ± 3.5 years) randomly assigned to a 6-8 RM load, 15-20 RM load, or a 30-40 RM load group. Participants completed a full body program (bench press, squats, triceps press-downs, bicep curls, and lat pulldowns) for 9 weeks, 3x/week, with reps to failure/set, and a moderate (2-3 min) rest between sets. The 6-8 RM group performed 3 sets/exercise; the 15-20 RM group performed 2 sets/exercise; and the 30-40 RM group completed 1 set/exercise. Results demonstrated that the 6-8 RM load group exhibited significantly larger increases in bench press 1RM strength and squat 1 RM strength, followed by the 15-20 RM group, and 30-40 RM group; however, the difference between groups was only statistically significant between the 6-8 RM load group and 30-40 RM load group. Additionally, although all groups exhibited statistically significant and similar improvements in absolute endurance strength, the 6-8 RM load group and 15-20 RM load groups exhibited a trend toward larger improvements in bench press absolute endurance (40 reps/minute to failure with a bench press load of 15.9 kg), and the 30-40 RM load group exhibited a trend toward larger increases in squat absolute endurance (40 reps/minute to failure with a squat load of 25 kg). Interestingly, all groups exhibited statistically significant and similar improvements in relative strength endurance (45% of pre-intervention bench press 1 RM load, and 55% of pre-intervention squat 1 RM load); however, it was the 6-8 RM load group and 30-40 RM load groups that exhibited trends toward the largest improvements (53). In summary, these studies suggest that if an increase in strength endurance is tested with light loads then performing reps-to-failure/set with lighter loads will result in larger improvements; however, if strength endurance is tested with significantly heavier loads, then training with heavier loads will result in larger improvements.

Two additional studies have implications for strength endurance routine design. Faigenbaum et al. (2001) compared 66 young children (age: 8.1 ± 1.6 years) randomly assigned to 1 of 5 groups completing a full body program and comparing different chest exercise routines. The groups included a control group (no intervention) a heavy load chest press group that performed 6-8 RM load/set and included chest press; a moderate load chest press group that performed 13-15 RM/set and included chest press; a heavy load and med ball chest pass group that performed 6-8 RM/set and included chest press and medicine ball chest pass, and a moderate medicine ball chest pass group that did not include chest press, but did include 13-15 RM/set load for med ball chest pass. All participants completed a full body program (chest, leg press, leg extensions, leg curls, hip abduction, pull-over, seated rows, crunches, and lat pulldowns) for 8 weeks, 2x/week, 1 set/exercise, and reps to failure/set. The results demonstrated that the intervention groups that included chest press exhibited a significant increase in chest press 1 RM strength, and the control group and the group only including med ball chest pass did not. Further, the moderate chest press group and heavy load chest press and med ball chest pass group exhibited a significant increase in strength endurance (completing as many reps as possible during chest press with pre-intervention 1 RM load) (68). Ratzin Jackson et al. compared 12 novice college-aged male exercisers who completed an "isolation quadriceps exercise on an exercise apparatus" with an endurance-then-strength protocol and a strength-then-endurance protocol in randomized order for 7.5 weeks, 4x/week, with 5.5 weeks of rest between protocols. The endurance protocol included 15-25% of 1-RM loads, 1 set/session, and continuous reps for 20-30 minutes, with a fast (20 reps/min) rep tempo. The strength protocol included 4 RM loads, reps-to-failure/set, with moderate (2 min) rest between sets. Both protocols were done during each session. The findings demonstrated that peak torque (measured at a velocity of 60°/sec) and endurance (measured via total work at a velocity of 180°/sec with 50% of peak torque) increased significantly following both protocols; however, significantly larger improvements were exhibited following the endurance-then-strength protocol (49). These studies may imply strength endurance is exercise-specific, and if strength endurance is the goal of training, endurance training should precede maximal strength training within a session.

Endurance

Power: Single Session Power Output

Power: Outcomes from Training with Various Loads

Power

Sample Program: Experienced Exerciser

        Training Load and Blood Chemistry

Fink, J., Kikuchi, N., & Nakazato, K. (2016).Effects of rest intervals and training loads on metabolic stress and muscle hypertrophy. Clinical physiology and functional imaging, 38(2), 261-268

Hakkinen, K., & Pakarinen, A. (1993).Acute hormonal responses to two different fatiguing heavy-resistance protocols in male athletes. Journal of Applied Physiology, 74(2), 882-887.

Schwab, R. O. B. E. R. T., Johnson, G. O., Housh, T. J., Kinder, J. E., & Weir, J. P. (1993). Acute effects of different intensities of weight lifting on serum testosterone. Medicine and science in sports and exercise, 25(12), 1381-1385.

Kraemer, W. J., Marchitelli, L., Gordon, S. E., Harman, E., Dziados, J. E., Mello, R., ... & Fleck, S. J. (1990). Hormonal and growth factor responses to heavy resistance exercise protocols. Journal of Applied Physiology, 69(4), 1442-1450.

Acute Variables: Training Load (Weight and Resistance)

Related Courses:

Course Summary: Acute Variables: Training Load (Weight and Resistance)

Course Study Guide: Acute Variables: Training Load (Weight and Resistance)

Course Summary Webinar: Training Load (Weight and Resistance)

Introduction: Acute Variables: Training Load (Weight and Resistance)

Research Findings
5 Sub Sections

Blood Chemistry

Cardiovascular Changes

Electromyographic (EMG) Activity

Bone Mineral Density

Rating of Perceived Exertion (RPE)

Body Composition

Hypertrophy
3 Sub Sections

Strength
5 Sub Sections

Endurance

Power
2 Sub Sections

Sample Program: Experienced Exerciser

Bibliography

Related Courses:

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Acute Variables: Training Load (Weight and Resistance)

Related Courses:

Course Summary: Acute Variables: Training Load (Weight and Resistance)

Course Study Guide: Acute Variables: Training Load (Weight and Resistance)

Course Summary Webinar: Training Load (Weight and Resistance)

Introduction: Acute Variables: Training Load (Weight and Resistance)

Research Findings5 Sub Sections

Blood Chemistry

Cardiovascular Changes

Electromyographic (EMG) Activity

Bone Mineral Density

Rating of Perceived Exertion (RPE)

Body Composition

Hypertrophy3 Sub Sections

Strength5 Sub Sections

Endurance

Power2 Sub Sections

Sample Program: Experienced Exerciser

Bibliography

Related Courses:

Comments

Guest

Research Findings
5 Sub Sections

Hypertrophy
3 Sub Sections

Strength
5 Sub Sections

Power
2 Sub Sections