Fixed Rest Periods Matched Gains in Less Time: New Study

Fixed rest periods of roughly 2–3 minutes produced similar lower-body muscle, strength, and endurance outcomes to self-selected rest in an eight-week study of trained adults—but the fixed-rest group finished workouts about 29% faster (Mohan et al., 2026).

That does not mean self-selected rest is ineffective. It means that, in this supervised lower-body program, waiting until lifters felt fully recovered did not produce a clear advantage that justified the extra training time.

• Fixed rest periods matched self-selected rest for muscle thickness and performance outcomes.
• Fixed-rest workouts averaged 56.0 minutes, versus 78.5 minutes with self-selected rest.
• Self-selected rest averaged 3.7 minutes between sets, compared with 2.4 minutes in the fixed-rest group.
• This was a SportRxiv preprint, so the findings are useful but still awaiting peer review.

Do Fixed Rest Periods Build Muscle as Well as Self-Selected Rest?

Fixed rest periods produced similar lower-body hypertrophy and performance changes to self-selected rest in this study, while requiring substantially less time (Mohan et al., 2026). For trained lifters who want efficient sessions, setting a timer may be a practical default rather than waiting until they subjectively feel ready.

In the 2026 SportRxiv preprint, Freedom of Choice? Effects of Self-Selected Rest Intervals on Muscular Adaptations and Time-Efficiency, Mohan and colleagues examined whether lifters benefit from choosing their own rest intervals.Readers can review the study’s preregistration and supplementary materials, which provide additional detail on the study plan and supporting files

Rest intervals matter because they affect both performance and session duration. Longer rests may feel more comfortable before another hard set, but more recovery is only useful if it improves the result enough to justify the added time.

How the Study Compared Rest Periods

The researchers randomly assigned 40 resistance-trained men and women, ages 18–40 years, to one of two groups for eight weeks.

• SELF group: 21 participants began their next set when they felt sufficiently recovered.
• FIXED group: 19 participants used prescribed rest intervals of approximately 2–3 minutes.

Both groups trained lower body twice weekly under supervision. Each session included Smith machine squats, leg extensions, standing calf raises, and seated calf raises. Participants performed four sets of 8–12 repetitions to volitional muscular failure for every exercise.

Researchers assessed muscle thickness in the quadriceps and calves, back-squat one-repetition maximum, knee-extension endurance, training volume, session rating of perceived exertion, and session duration. Participants could not use phones or converse with others in the training area, reducing common distractions that can stretch rest periods in commercial gyms.

Fixed Rest Periods Produced Similar Adaptations

Both groups increased muscle thickness. Across measured sites, the authors reported approximate quadriceps increases of 5.3% to 9.9% and calf increases of 8.3% to 19.1%.

Back-squat strength improved by 20.8% in SELF and 17.3% in FIXED.

Knee-extension endurance also improved in both groups. SELF improved by 29.6% and FIXED by 16.6%.

Fixed Rest Periods Cut Workout Time

The biggest practical difference was session duration. Fixed-rest participants completed training in 56.0 ± 4.5 minutes, while self-selected-rest participants averaged 78.5 ± 15.4 minutes per session.

Within this supervised lower-body program, fixed rest was approximately 29% more time-efficient. The estimated gap increased from 19 minutes in week 1 to 32 minutes in week 8.

The explanation is straightforward: the FIXED group averaged 2.4 ± 0.3 minutes between sets, whereas the SELF group averaged 3.7 ± 1.2 minutes. Training volume and session RPE were similar between groups, so the longer sessions did not clearly translate into more productive work.

What This Means for Your Training

If your goal is efficient hypertrophy-focused training, start by using fixed rest periods rather than relying entirely on how recovered you feel.

• Use roughly 2–3 minutes after demanding compound lower-body sets.
• Use about 2 minutes after hard machine or isolation work.
• Extend rest when performance is meaningfully declining, a set is unusually demanding, or you are managing fatigue or discomfort.
• Do not assume that feeling completely recovered before every set will automatically produce better gains.

Self-selected rest was not ineffective in this study. It simply did not show a clear advantage over fixed rest despite making sessions longer.

Limitations

This evidence should be interpreted cautiously. The study lasted only eight weeks, used young recreationally trained adults, and focused exclusively on lower-body training performed twice per week (Mohan et al., 2026).

The controlled environment also limits real-world generalizability: participants were supervised and could not socialize or use phones. Dietary intake was assessed through self-reported food records, which can introduce error (Mohan et al., 2026).

Most importantly, this is a preprint rather than a peer-reviewed publication. The findings are promising, but they should not be treated as the final word on rest intervals.

Conclusion

Fixed rest periods of approximately 2–3 minutes matched self-selected rest for lower-body muscle thickness, strength, and endurance changes in this eight-week preprint, while reducing average session duration by about 29% (Mohan et al., 2026).

For most trained lifters, a timer is a sensible default: use enough rest to maintain high-quality sets, but do not add extra minutes unless they are clearly helping your performance.

FAQ

Are fixed rest periods better for muscle growth?

Fixed rest periods were not clearly better for muscle growth in this study. They matched self-selected rest for measured muscle-thickness changes while allowing participants to finish workouts substantially faster. Because this was an eight-week preprint in trained adults, the finding should not be generalized to every population or program (Mohan et al., 2026).

How long should I rest between sets for hypertrophy?

Fixed rest periods of about 2–3 minutes are a practical starting point for hypertrophy-focused lower-body training. In this study, that range supported similar adaptations to longer self-selected rest. You may need longer intervals for highly demanding compound lifts or when performance drops sharply (Mohan et al., 2026).

Is self-selected rest bad for training?

Self-selected rest intervals were not harmful in this study. Participants improved muscle thickness, strength, and endurance. The tradeoff was time: self-selected sessions averaged 78.5 minutes compared with 56.0 minutes with fixed rest, without a clear outcome advantage (Mohan et al., 2026).

Did longer rest improve strength?

Fixed rest periods and self-selected rest produced similar strength outcomes in the adjusted analyses. Squat one-repetition maximum increased 20.8% with self-selected rest and 17.3% with fixed rest, but the pooled performance estimate showed no clear between-group advantage (Mohan et al., 2026).

Should I use a timer between sets?

Fixed rest periods are worth using if you value predictable, time-efficient workouts. A timer can prevent rest intervals from drifting longer than necessary while still allowing sufficient recovery for hard sets. Adjust the interval when your exercise selection, fatigue, or performance data justify it.

Medical Disclaimer

This article is for informational purposes only and is not a substitute for individualized medical, training, or nutritional advice. Consult a qualified healthcare professional before changing your exercise program.

References

Mohan, A. E., Piñero, A., Coleman, M., Hopper, A., Segtnan, R., Montenegro, D., Hermann, T., Androulakis Korakakis, P., Wolf, M., Swinton, P. A., & Schoenfeld, B. J. (2026). Freedom of choice? Effects of self-selected rest intervals on muscular adaptations and time-efficiency [Preprint]. SportRxiv. Preregistration | Supplementary materials

About the Author

Robbie Durand

Robbie Durand is an exercise physiologist and science writer specializing in evidence-based fitness and nutrition research. With over 15 years of experience translating peer-reviewed studies into actionable advice, Robbie helps readers make informed decisions about training, supplementation, and body composition.