Short, 20-Second Rest Intervals Just As Good As 2-Minutes Rest (When Volume is Matched)
The study finds no difference in muscle growth between 20-second and 2-minute rest periods.
What if the length of time you rest between sets doesn’t matter as much as you think? This new research challenges conventional training lore, which has long emphasised longer rest periods for maximising muscle growth and strength gains. It turns out, rest interval durations can be a little more flexible than we thought. There is a caveat, though.
This study by Attarieh and colleagues (2025) directly compared ultra-short 20-second rest intervals against standard 2-minute rest periods in a 10-week resistance training program. The twist: both groups performed the same total work (volume-load), but the short-rest group had to complete significantly more sets to match the longer-rest group’s repetition count. The findings challenge common assumptions about rest intervals and offer practical implications for anyone trying to build muscle or strength efficiently.
Aim
To determine whether inter-set rest interval duration influences muscle hypertrophy and maximum strength gains when training volume-load (repetitions × sets × load) is equated between protocols. Researchers hypothesised that both very short (20 seconds) and long (2 minutes) rest intervals would produce similar adaptations when total work performed was matched.
Methods
Seventeen untrained young men (average age 25.3 years) participated in a within-subject design where each participant trained one leg with short rests and the other with long rests twice-weekly for 10 weeks. The long-rest (LONG) protocol involved 3–4 sets of 10-repetition maximum (10RM) exercises performed to failure with 2-minute rest intervals. The short-rest (SHORT) protocol used the same 10RM load but with only 20-second rest intervals, requiring participants to perform multiple sets until they matched the total number of repetitions completed in the LONG condition. This resulted in the SHORT group performing an average of 5.6 sets compared to 3.4 sets for LONG, but completing sessions in approximately half the time (3 minutes 10 seconds versus 7 minutes 19 seconds). Quadriceps muscle growth was assessed using MRI scans to measure cross-sectional area at three different regions of the thigh, and maximum strength was evaluated through unilateral knee extension one-repetition maximum (1RM) testing.
Results
Both training protocols produced substantial and statistically equivalent improvements in muscle size and strength. For total quadriceps cross-sectional area, the SHORT condition increased by 8% while LONG also increased by 8%, with no significant difference between conditions. When examining individual muscle regions, the rectus femoris increased by 14.3% with SHORT and 16.7% with LONG, while the vastii muscles increased by 7.2% with SHORT and 6.4% with LONG—none of these differences reached statistical significance. Maximum strength improvements were virtually identical, with SHORT producing a 42.4% increase and LONG a 41.5% increase in unilateral knee extension 1RM performance. Importantly, total training volume-load was successfully matched between conditions throughout the 10-week intervention (SHORT: 1,536.5 kg; LONG: 1,672.9 kg), confirming that any differences in outcomes would be attributable to the rest interval manipulation rather than differences in total work.
Practical Takeaways
For people with limited training time, the SHORT protocol offers significant efficiency advantages, achieving the same muscle and strength gains in less than half the session duration. However, the tradeoff is performing 60% more sets (5.6 versus 3.4 sets on average) to compensate for the reduced repetitions per set that occur with shorter rest periods.
Conversely, those who prefer shorter workouts with fewer total sets can benefit from longer rest intervals, which allow more repetitions to be completed per set and thus require fewer sets overall to achieve the same volume-load. The key insight is that when transitioning between rest interval strategies, lifters should monitor and adjust their total volume-load—whether through training apps or manual tracking—to ensure comparable training stimulus. Simply shortening rest without compensating with additional sets will reduce total work and potentially compromise results.
What Does This Look Like in Practice?
If you want to reduce your rest periods but maintain your training effectiveness, you need to understand how to match volume-load across your workouts. Volume-load is calculated as: repetitions × sets × load.
Here’s an example from the study:
With 2-minute rest intervals, participants completed an average of 3.4 sets per session, performing roughly 10 repetitions per set to failure. When switching to 20-second rest intervals with the same load, they had to perform 5.6 sets on average to accumulate the same total number of repetitions, since shorter rest meant fewer reps per set. This resulted in approximately 65% more sets but took less than half the time (3 minutes 10 seconds versus 7 minutes 19 seconds).
Step-By-Step Application
Track your current program: Record the total repetitions, sets, and load for each exercise over a session or week using a training app or notebook
Calculate your baseline volume-load: Multiply reps × sets × load for each exercise to establish what you’re currently doing
When shortening rest periods: Expect to complete fewer reps per set, so add additional sets until you reach the same total repetition count
Monitor performance: If your first set with the new rest scheme hits 10 reps but subsequent sets drop to 6–7 reps, keep adding sets until your total reps match your previous program
Adjust load if needed: The intensity of load (%1RM) should remain similar between protocols—only the set structure changes to compensate for the reduced per-set volume
The critical point is that simply cutting rest time without compensating with additional sets will reduce your total volume-load and potentially compromise results. However, if you systematically track and match your total work, you can choose rest intervals based on time constraints or preference without sacrificing muscle or strength gains.
Key Takeaways
This study provides evidence that inter-set rest interval duration may not meaningfully influence muscle hypertrophy or maximum strength gains when total volume-load is equated in untrained people performing high-intensity resistance training. The findings align with previous research suggesting that volume-load is a critical determinant of training adaptations, and that different rest interval strategies can be adjusted to match this external training demand. While 20-second rest intervals required more sets to match the work of 2-minute intervals, both protocols produced equivalent 8% increases in quadriceps size and 42% increases in knee extension strength over 10 weeks. These results challenge traditional recommendations that prioritise longer rest periods for hypertrophy and strength, suggesting instead that rest interval selection can be based on individual preferences, time constraints, or training goals, provided total volume-load remains consistent.
Reference
Attarieh, Parsa & Nunes, J.P. & Negahdar, Saman & Khani, Saeed & Goli, Amirali & Fallah, Mohammad Hossein & Nazarirad, Hamed & Nazari Rad, Shahriar & Mojtahedi, Shima & Soori, Rahman. (2025). Comparison between 20-s and 2-min inter-set rest intervals on changes in muscle cross-sectional area and maximum strength under volume-load-equated resistance training. Sport Sciences for Health.
You can also find me at dannyleejames.com for stories, personal training insights, and coaching.