Effect of Different Inter-set Rest Intervals on Muscle Performance During Leg Press Exercise in Trained Older Women

Research Review: Effect of Different Inter-set Rest Intervals on Muscle Performance During Leg Press Exercise in Trained Older Women

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

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

Original Citation:

Jambassi Filho, J., Gobbi, L., Gurjao, A., Goncalves, R., Prado, Alexandre, and Gobbi, S. (2013). Effect of different rest intervals, between sets, on muscle performance during leg press exercise, in trained older women. Journal of Sports Science and Medicine, (12), 138-143. Abstract

Why the Study Is Relevant:

Previous research has demonstrated that longer (2- to 3-minute) inter-set rest periods promote a greater number of repetitions than shorter (1-minute or less) inter-set rest periods in younger and older women, regardless of whether the exercise was lower-body, upper-body, multi-joint or single-joint (1,2). Prior to this 2013 study, the influence of inter-set rest periods on lower limb performance in older women with resistance training experience was unknown. Researchers investigated the influence of 1- and 3- minute inter-set rest periods during multiple sets of leg press. Data was gathered on the total number of repetitions, sustainability of repetitions and total volume during each resistance training session. The findings suggest that longer (3-minute) inter-set rest periods are better for work-out performance.

Caption: Demonstration of Leg Press Machine Exercise

By No machine-readable author provided. GeorgeStepanek assumed (based on copyright claims). - No machine-readable source provided. Own work assumed (based on copyright claims)., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=42922

Study Summary

Study Design	Randomized, counterbalanced, within-subjects design
Level of Evidence	IIB Evidence from at least one other type of quasi-experimental study
Subject Characteristics	Demographics: Age: 68 +/- 5.9 yrs Gender: Female Number of participants: 17 Inclusion Criteria: Resistance training experience Participation in a specified 8-week resistance training program, as described below Exclusion Criteria: Cardiovascular and other physiological disorders Neurological disorders that may increase risk or affect results Completed less than 80% of the 8-week resistance training program
Methodology	All participants used the horizontal leg press machine (Righetto Fitness Equipment; Campinas, SP, Brazil) with adjustable weight stacks. The knee and hip angles were adjusted to 90˚ and 110˚, respectively. This position was recorded and used in all testing sessions. Only full range of motion (ROM) repetitions were counted. Pauses between concentric and eccentric phases were not allowed; pauses between reps were allowed. All participants were verbally encouraged for maximum effort. Participants attended 5 sessions in the lab, with 48 to 72 hours between each session. Sessions 1-3 followed the same protocol to determine the load for the 15-repetition maximum (RM) to be used in sessions 4 and 5 (the two testing sessions): A warm-up of one set of 10 reps at 50% of the estimated 15 RM based on training loads, a 30-second rest, and then as many reps as possible until perceived exhaustion. Sessions 1-3 included a maximum of 3 trials/session with 10-minute inter-set rest periods. Sessions 1 and 2 were used to determine the load, and session 3 was used to retest and verify the load for for the 15 RM testing. Sessions 4 and 5 followed the same warm-up and exercise protocol (3 sets of 15 RM until perceived exhaustion), but used 1-minute or 3-minute inter-set rest periods based on the randomized, counter-balanced design. The number of reps completed in each set was recorded. The number of reps in the first set of each testing session was expressed as a percentage of the repetition target (15 RM). Additional measures were calculated and are listed in the Outcome Measures section. Participants attended sessions at the same time each day (from 7:00 a.m. to 9:00 a.m.). Participants were instructed to maintain normal diets and hydration status. Participants were instructed to refrain from intense physical activity and alcohol consumption for 24- and 48- hours before their sessions, respectively. Prior to the study, participants completed a supervised 8-week resistance training program that included 8 exercises, 3 days per week. The exercises alternated body segments and included the leg press. The exercises also included 3 sets of 70% of the participants' 15 RM. The training program used 2-minute inter-set rest periods.
Data Collection and Analysis	A 2-way ANOVA was used to measure the effects of different inter-set rest periods on the total number of repetitions (NR), sustainability of reps, duration of sets (DS) and average time for each repetition (DS/NR). A Scheffe post-hoc analysis was used when necessary to further analyze two variables. A paired student-t test was used to measure differences in the total volume and number of reps, duration of sets, and DS/NR totals between 1- and 3-minute inter-set rest periods. Statistical significance: P = 0.05 ICC (0.82) was used to test the reliability of the 15 RM assessments.
Outcome Measures	Total number of repetitions Counted and recorded, expressed as a percentage of repetition target (15 RM) Duration of set 1 second in concentric phase and 2 seconds in eccentric phase Time from onset of first rep to perceived exhaustion was recorded manually with a digital timer. Total average time for each repetition (DS/NR) Repeated for all 3 sets. Sustainability of repetitions (number of reps in 2nd set x 100) / (number of reps in 1st set) (number of reps in 3rd set x 100) / (number of reps in 1st set) Total volume of each testing session (4 and 5) sum of all reps x load
Results	Total number of repetitions Both inter-set rest periods corresponded with decreased total number of reps in set 2 and set 3. The 3-minute inter-set rest period corresponded with 30% more total reps than the 1-minute inter-set rest period. Duration of set Both inter-set rest periods corresponded with decreased time to perceived exhaustion in subsequent sets. The 3-minute inter-set rest period corresponded with 28.3% greater total time under tension than the 1-minute inter-set rest period. Total average time for each repetition (DS/NR) There was no difference between 1-minute and 3-minute inter-set rest periods. 1-minute inter-set rest period produced greater duration of each repetition in the second and third sets. Sustainability of sets The sustainability of reps from the first set to the second and from the first set to the third decreased after both 1-minute and 3-minute inter-set rest periods. The sustainability of reps from the second set to the third decreased after the 3-minute inter-set rest period but was unchanged after the 1-minute rest period. The 3-minute inter-set rest period was followed by higher sustainability in the second and third sets than the 1-minute rest period. Total volume The 3-minute inter-set rest period corresponded with 29.4% more total volume than the 1-minute inter-set rest period.
Our Conclusions	The findings suggest that longer (3-minute) inter-set rest periods are required to maintain muscle performance from set to set during low-load, lower body resistance training sessions for older women with resistance training experience.
Researchers' Conclusions	3-minute inter-set rest periods allowed participants to better maintain total reps, time under tension, speed of repetition and volume of each set, resulting in a nearly 30% increase in total volume during the training session.

Caption: Back Squat Technique

Squat Technique

Review & Commentary

This study investigated the influence of 1- and 3-minute inter-set rest periods on muscle performance in resistance trained older women during multiple sets of the leg press. The findings suggest that longer (3-minute) inter-set rest periods are necessary to achieve greater muscle performance, as measured by maintaining the number of repetitions, time under tension and total volume across multiple sets.

This study had many methodological strengths, including:

Randomization of the order of the inter-set rest periods minimized the training effects on subsequent sessions.
Standardized procedures and controlling of external variables enhance the strength of study results.
For this population (older women), the use of a low-load, machine based program adds to the practicality of the research findings.

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

Only 1- and 3-minute inter-set rest periods were studied. The lack of testing on additional inter-set rest periods may make it difficult to construct detailed guidelines or protocols based on research findings.
The exercises used in the pre-study resistance training program were not listed. This information would help provide context about the participants' training status.
Muscular adaptations, such as strength and hypertrophy, were not measured. Future studies should build on this research by investigating these and other adaptations.

How This Study Is Important:

This study adds to a growing body of research on inter-set rest period length. Recent studies are trending toward longer, 2 and 3 minute rest intervals. As found in this study, longer rest intervals result in better maintenance of performance from set to set and increased volume per training session. Aggregation of the findings from these studies should aid in the creation of more refined guidelines for inter-set rest period length.

How the Findings Apply to Practice:

The findings suggest that 3-minute inter-set rest periods improve performance from set-to-set in lower body resistance-training programs for trained older women. Human movement professionals should consider using longer inter-set rest periods (3 minutes) to increase the total number of repetitions and time under tension per set, and the total volume of training sessions.

It is presumed that the increase in volume and performance from set to set will impart a larger stimulus for adaptation. This could result in better outcomes over-time, or fewer sessions to set strength goals. As this study was performed on older women, it may be worth noting that this increase in stimulus may not pose the same risk as increased load.

How Does It Relate to Brookbush Institute Content?

The Brookbush Institute encourages practitioners to consider all variables of program design, and to individualize acute variables based on available best-evidence, client needs and goals. The common recommended range for inter-set rest periods is 1- to 3-minutes, depending on the training phase. This study demonstrates that a 3-minute inter-set rest period increased the total number of repetitions and time under tension per set, and the total volume of exercise per training session for low-load (15 RM), lower-body exercise in trained older women. This may imply that recommendations for inter-set rest period should be longer, should be longer for lower body exercise, or that inter-set rest periods should increase as we age. The Brookbush Institute will consider all of these implications in the continued pursuit of optimal guidelines, as we aggregate findings from all available research and practice.

The following videos illustrate other exercises that could be used for lower body training in older women:

Squat

Squat to Row

Front Squat

Bibliography:

Willardson, J., and Burkett, L. (2006). The effect of rest interval length on the sustainability of squat and bench press repetitions. Journal of Strength and Conditioning Research, 20, 400-403.
Jambassi Filho, J., Gurjao, A., Goncalves, R., Barboza, B., and Gobbi, S. (2010). The effect of different recovery intervals between sets of strength training on muscular force in trained older women. Brazilian Journal of Sports Medicine, 16, 113-116. (In Portuguese: English abstract)

Questions, comments, and criticisms are welcomed and encouraged -

Effect of Different Inter-set Rest Intervals on Muscle Performance During Leg Press Exercise in Trained Older Women

Research Review: Effect of Different Inter-set Rest Intervals on Muscle Performance During Leg Press Exercise in Trained Older Women

Bibliography:

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