How long a break is needed between sets during strength training?

The time that elapses between two training sets is called the rest period or interval. The American College of Sports Medicine recommends [1] rest periods ranging from 1 to 2 minutes for 6 rm to 12 rm, 3 to 5 minutes for strength training with fast contraction speeds, and under 90 seconds for local muscular endurance training with light to medium loads and more than 15 reps.

The science

Ratamess and colleagues examined the effect of different rest periods on the metabolism during bench presses. Eight men with experience in strength training (21.4 ± 2.4 years old) performed 10 randomised protocols (5 sets of bench presses at 75 % and 85 % of 1-RM for 10 and 5 reps, respectively) with rest periods of varying lengths (30 s, 1, 2, 3, 5 min). The most important finding was that performance at both load intensities worsened as the rest periods were reduced. For participants doing 10 reps, the 30-second rest period decreased the total exercise volume by more than 24 % compared to the group who took a 5-minute rest period.

Ahtiainen’s research team [3] addressed the question of how short and long rest periods impact strength, muscle size and hormonal changes within the quadriceps. Thirteen strength-training-experienced men (28.7 ± 6.2 years old) participated in the study. They formed two training groups consisting of two different rest periods (short: 2 minutes, or long: 5 minutes). After three months of training, the groups were swapped. The participants in the short group then trained using a longer rest period, and vice versa.

Here’s what the training protocol looked like:

• Short rest period group 5 sets on the leg press, 4 sets of squats, both at 10 reps per set
• Long rest period group 5 sets on the leg press, 4 sets of squats, both at 10 reps per set In addition, the load was increased by approximately 15 % to equalise the training volume between groups.

When measured at 0, 3 and 6 months, the strength of the quadriceps didn’t differ significantly between groups. MRI scans of the cross-sectional area of the quadriceps muscle showed a significant increase on the baseline of 3.5 ± 4.3% in both groups after 6 months. After three months, the measurement showed the cross-section of the quadriceps muscle indicated no significant difference between groups.

Two studies on the topic

De Souza and colleagues [4] examined muscle strength and hypertrophy between constant and decreasing rest intervals during eight weeks of strength training. Twenty strength-training-experienced young men (20.5 ± 1 years) were randomly assigned to either a constant-rest group or a decreasing-rest group. During the first 2 weeks of training, both groups performed 3 sets of 10 to 12 reps with 2-minute rest periods between sets and exercises. Over the following six weeks, the group assigned a constant rest period could take a two-minute rest period between sets and exercises (4 sets, 8-10 RM). Meanwhile, the group assigned a decreasing rest period started off with a 2-minute rest, which went down to 30 seconds. They also did 4 sets at 8-10 RM. As a result, the total training volume for bench presses and squats was significantly lower in the group with decreasing rest than in the group with constant rest (bench press 9.4%, squat 13.9%). Magnetic resonance imaging was used to examine the muscle cross sections of each group. No significant differences were observed between the two groups in terms of muscle cross-sectional area (arm 13.8 % vs. 14.5 %, thighs 16.6% vs. 16.3 %), the 1-RM (bench press 28 % vs. 37 %, squats 34 % vs. 34 %) and the isokinetic peak torque.

Schoenfeld et al. [5] studied adaptations to strength training in 21 young, athletic men between 18 and 35, who were randomly assigned to either a 1-minute rest group or a 3-minute rest group. The total training volume was equal. Over the course of the 8-week study, participants completed three full-body workouts per week. These involved three sets of 8 to 12 reps of seven different exercises per workout. Their muscle strength was tested using the 1-RM in bench presses and squats, while muscle thickness of the elbow flexors, m. triceps brachii and m. quadriceps femoris was measured using an ultrasound. The researchers discovered a greater increase in the 1-RM of bench presses and squats among the 3-minute-interval group in comparison with the 1-minute-interval group. Although there was no significant difference, a trend toward a greater increase in m. triceps brachii thickness (P = 0.06) was noted for the group with the longer rest interval.

Conclusion

To sum up, rest periods influence the total exercise volume and represent a trade-off between mechanical tension and metabolic stress. On the other hand, the current literature suggests that rest periods have little effect on strength and hypertrophy when total training volume is monitored.

References

1. ACSM, American College of Sports Medicine. Progression models in resistance training for healthy adults. Med Sci Sports Exerc. United States; 2009;41: 687–708. doi:10.1249/MSS.0b013e3181915670
2. Ratamess NA, Falvo MJ, Mangine GT, Hoffman JR, Faigenbaum AD, Kang J. The effect of rest interval length on metabolic responses to bench press exercise. Eur J Appl Physiol. Springer; 2007;100: 1–17. doi:10.1007/s00421-007-0394-y
3. Ahtiainen JP, Pakarinen A, Alen M, Kraemer WJ, Häkkinen K. Short vs. long rest period between the sets in hypertrophic resistance training: Influence on muscle strength, size, and hormonal adaptations in trained men. J Strength Cond Res. United States; 2005;19: 572–582. doi:10.1519/15604.1
4. De Souza TP, Fleck SJ, Simão R, Dubas JP, Pereira B, De Brito Pacheco EM, et al. Comparison between constant and decreasing rest intervals: Influence on maximal strength and hypertrophy. J Strength Cond Res. 2010;24: 1843–1850. doi:10.1519/JSC.0b013e3181ddae4a
5. Schoenfeld BJ, Pope ZK, Benik FM, Hester GM, Sellers J, Nooner JL, et al. Longer interset rest periods enhance muscle strength and hypertrophy in resistance-trained men. J Strength Cond Res. 2016;30: 1805–1812. doi:10.1519/JSC.0000000000001272