Facebook Pixel
Brookbush Institute Logo

Tuesday, June 6, 2023

Acute and Long-term Responses to Different Inter-set Rest Periods in Low-load Resistance Training

Brent Brookbush

Brent Brookbush


Research Review: Acute and Long-term Responses to Different Rest Intervals in Low-load Resistance Training

By Crystal Chariton MA, LMT, CSCS, NASM-CPT, USAW

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Fink, J., Schoenfeld, B., Kikuchi, N., & Nazakato, K. Acute and long-term responses to different rest intervals in low-load resistance training. International Journal of Sports Medicine. Int J Sports Med. 2017; 38(02): 118-124. ABSTRACT

Why the Study is Relevant: Inter-set rest period and load are two commonly adjusted variables in resistance training programs designed to increase hypertrophy and strength. Conflicting evidence exists regarding whether shorter or longer inter-set rest periods results in greater muscular adaptations (1-4). There is also conflicting evidence on whether low-load training can result in similar muscular adaptations as high load training (4, 5). This 2017 study by researchers from Nippon Sport Science University in Tokyo offers evidence that training with low-loads to failure results in the same post-exercise hormone response, hypertrophy and strength gains regardless of rest period length. Further, the adaptations to low-load training would seem to be similar to those reported in studies using high-load training.

Dr. Brookbush instruct Laura DeAngelis on proper form for a Bench Press
Caption: Dr. Brookbush instruct Laura DeAngelis on proper form for a Bench Press

Bench Press

Study Summary

Study Design Cohort study. Findings are based on two independent experiments, as detailed below.
Level of EvidenceIIA evidence from at least one controlled study without randomization
Subject Characteristics
  • Age: 18-22
  • Gender: not specified
  • Number of participants: 14 in Experiment 1; 21 in Experiment 2
  • Athletes, not specified

Inclusion Criteria:

  • Regular exercise for different sports
  • No resistance training for at least two years prior
  • No other strength training throughout the duration of the study

Exclusion Criteria:

  • None listed
MethodologyExperiment 1:
  • One week prior to the start of the experiment, a 1 rep max (1RM) was determined for each subject for the bench press and back squat. This was used to establish a training load of 40% for each exercise.
  • The subjects were divided into 2 groups: the short rest (S) group performed 30-second inter-set rest periods; the long rest (L) group performed 150-second inter-set rest periods.

  • Both groups performed 4 sets of bench press followed by 4 sets of back squats, with a 1 second concentric and 2 second eccentric contraction. Qualified personal trainers supervised each session to ensure proper technique.
  • Each set was performed until failure, defined as an "inability to perform another concentric repetition while maintaining proper form."
  • Blood samples were drawn from the antecubital vein with a winged static injection before, immediately after, 15 minutes after, 30 minutes after and 60 minutes after the sessions.

Experiment 2:

  • Same exercise protocol was used as Experiment 1; however, training was held 2 times per week for 8 weeks and blood samples were not collected.

Subjects in both experiments were asked to maintain their usual eating habits during the experiment. To equalize post-training food intake, subjects drank a standardized protein shake immediately after each workout.


Outcome MeasuresExperiment 1:
  • Growth hormone (GH), Insulin-like growth factor 1 (IGF-1), and Testosterone (T)
  • GH and T were assessed via the electrochemiluminescence method
  • IGF-1 was assessed via the immunoradiometric assay
  • Total training volume for each exercise during a single session was recorded

Experiment 2:

  • MRI (magnetic resonance imaging) measured the muscle cross-sectional area (CSA) of the right upper arm and thigh of each subject the week before the training program and the week after the last session.
  • Subjects performed 2 standardized warm-up sets
  • 1RM was assessed within 5 reps with a 3-minute rest between sets for each subject
  • Bench press 1RM: The bench press was successful if the barbell was in a full lock-out position with head, upper back and buttocks on the bench and both feet flat on the floor.
  • Back squat 1RM: The squat was successful if the subject reached parallel.
  • Total training volume for each exercise during and after each training session was recorded.

A reliability test showed intraclass correlation coefficient (ICC) of >0.9 for CSA calculations

1RM measurements had ICC of >0.9

ResultsExperiment 1:
  • Both groups showed significant (p<0.05) increases in growth hormone (GH; 33.7 - 33.8 ug/L) and insulin-like growth factor 1 (IGF-1; 27.7 - 29.9 ug/L) immediately post workout
  • There was no significant change in testosterone
  • The short rest group had reduced volume in sets 2-4 (p<o.o1)

Experiment 2:

  • Cross-sectional area (CSA) of triceps and thigh increased in both groups; no significant between group differences
  • Triceps CSA in short rest group: Increased 9.8±8.8%
  • Triceps CSA in long rest group: Increased 10.6±9.6%
  • Thigh CSA in short group: Increased 5.7±4.7%
  • Thigh CSA in long rest group: Increased 8.3±6.4%
  • The increase in CSA of the thigh had a larger effect size for longer rest periods than for shorter rest periods (0.93 vs. 0.58)
  • Both groups significantly increased bench press 1RM (S: 9.9 ± 6.9%, L: 6.5±5.8%, p<0.05) and back squat 1RM (S: 5.2 ± 6.7%, L: 5.4±3.5%, p<0.05)
  • The training volume was significantly greater in the long rest group for each resistance training session and exercise
Our Conclusions

Low-load resistance training, using either short or long inter-set rest periods, results in similar gains in hypertrophy and strength. Immediate increases of post-exercise GH and IGF-1 were also similar.

Further, the results of this study are similar to studies using high-load training protocols.

Researchers' ConclusionsWhen performing low-load resistance training to failure, increases in GH and IGF-1 are similar immediately post-workout whether short or long rest periods are used. Cross-sectional area and strength also increase in both the long and short rest period groups with no significant difference in 1RM bench press or back squat strength.

Low-load back squat sets to failure produce similar results regardless of interset rest duration
Caption: Low-load back squat sets to failure produce similar results regardless of interset rest duration

Low-load back squat sets to failure produce similar results regardless of inter-set rest duration

Review & Commentary

This study investigated the effects of short (30-second) and long (150-second) inter-set rest periods during low-load (40% of 1RM) resistance training to failure. Researchers compared acute and longitudinal data from two independent experiments, filling a gap in the literature. Acute hormonal responses as well as the changes in muscle size and strength were measured after an 8-week training period, producing similar results in both groups. When Designing training programs, shorter interest rest periods can minimize training time and thus time spent in the gym.

The methodological strengths included:

  • The methodology was well documented. Both experiments followed similar standardized protocols. Confounding variables, such as nutrition, were addressed by encouraging participants to maintain their regular eating habits (with the exception of a standardized post-workout shake). The participants were also asked to refrain from any other strength training for the duration of the study.
  • The use of MRI to measure cross-sectional area reflected whole muscle hypertrophy, and is likely more reliable than anthropometric measurements.
  • Selecting exercises commonly used to promote muscle strength and hypertrophy increased the relevance and practicality of the study.
  • The researchers used the same training protocols to examine 2 sets of data. This eloquent design should be adopted by more researchers, as it allows for the comparison, or integration, of two sets of data.

Weaknesses that should be noted prior to clinical integration of the findings included:

  • A small sample size was used; a larger sample size may show statistically significant differences between groups.
  • Gender was not identified, although it was likely an all male sample based on the numbers related to testosterone. Hormone response, hypertrophy and strength gains vary a great deal between men and women; this study may be of little consequence when designing programs for females.
  • The selection of participants for short-rest or long-rest groups was not explained.
  • Subjects had not trained for a minimum of 2 years. It is plausible that the increases in hypertrophy and muscular strength were due to the introduction of a resistance training program and had little to do with the variable measured. Further, the results may not reflect those changes expected from an experienced strength training population.
  • Hormone testing post exercise was not performed at the end of the 8 week training program. Comparing the elevation in hormones at the beginning and end of the research study may have provided further information on how the body adapts to an exercise routine.
  • Although 8 weeks is a significant amount of time for a research study, training programs are often much longer. Longer studies are desperately needed in this field, as well as similar studies on those individuals with training experience.

How This Study is Important: This study adds to a growing body of research that challenges conventional wisdom regarding inter-set rest period length and ideal loads for hypertrophy and strength gains. In this study, the duration of inter-set rest periods during low-load resistance training to failure did not effect the immediate post-exercise increases in GH or IGF-1, and similar gains were noted in both short and long inter-set rest period groups for hypertrophy and strength post 8 weeks of training. The fact that strength and hypertrophy gains were noted in this study, challenges the convention that larger loads should be lifted to optimize strength and hypertrophy gains.

How the Findings Apply to Practice:

When designing a resistance training program consider the following. Sets of low-load (40% of 1RM) resistance training to failure will result in an increase in GH, IGF-1, strength and hypertrophy in the novice or deconditioned individual. This may imply that heavier loads are not necessary during the initial training period. Further, when incorporating low-load resistance training to failure into a program, short or long rest periods result in similar benefits. If the client/patient tolerates shorter rest times, it may be possible to decrease the total length of a session.

How does it relate to Brookbush Institute Content?

The Brookbush Institute (BI) stresses the importance of considering all acute training variables when designing a rehab, fitness or performance training program, including inter-set rest periods. BI refers to low-load training during "Endurance Training" and/or "Stability Training" phases. Findings from this study suggest that shorter inter-set rest periods are sufficient for optimizing benefits of Endurance and/or stability training. As a practical education company, BI realizes that efficiency may be as important as efficacy; as human movement professionals are often faced with the challenge of multiple objectives, and/or limited session times. Shorter rest periods may reduce overall session time without impacting results, or allow more objectives to be addressed in a single session. Further, this study may imply that all individuals should start with "Endurance/Stability" training, as it is sufficient for increasing strength and muscle hypertrophy in novice, and/or deconditioned clients/patients, and low-loads may pose less risk than large-loads. This study only included two main exercises, the bench press and back squat, and did not address circuit training, which BI commonly uses to reduce overall session time.

The following videos are related to the exercises used in this study.

Back Squat


Bench Press

Stability Ball Push-up


  1. Villanueva MG, Lane CJ, Schroeder ET. Short rest interval lengths between sets optimally enhance body composition and performance with 8 weeks of strength resistance training in older men. Eur J Appl Physiol. Feb 2015; 115(2): 295-308.
  2. Henselmans M, Schoenfeld BJ. The effect of inter-set rest intervals on resistance exercise-induced muscle hypertrophy. Sports Med. Dec 2014; 44(12): 1635-1643.
  3. Buresh R, Berg K, French J. The effect of resistive exercise rest interval on hormonal response, strength, and hypertrophy with training. J Strength Cond Res. 2009: 23: 62-71.
  4. Schoenfeld BJ, Pope ZK, Benik FM, Hester GM, Sellers J, Nooner JL, Schnaiter JA, Bond-Williams KE, Carter AS, Ross CL. Longer interset rest periods enhance muscle strength and hypertorphy in resistance-trained men. J Strength Cond Res. 2015; 30: 1805-1812.
  5. Burd NA, West DWD, Staples AW, Atherton PJ, Baker JM, Moore DR, Holwerda AM, Parise G, Rennie MJ, Baker SK. Low-load high volume resistance exercise stimulates muscle protein synthesis more than high-load low volume resistance exercise in young men. PLOS One 2010; 5: e12033

© 2017 Brent Brookbush

Questions, comments, and criticisms are welcomed and encouraged.