How long should I rest between sets?
It has long been believed that the metabolic demands of shorter rest periods produced greater gains in muscular hypertrophy than longer rest periods. The general rest period recommendation for bodybuilders looking to optimize hypertrophy training is 1 minute or less. Brad Schoenfeld and his team put this “established” rest period recommendation to the test.
Schoenfeld, B. J., et al. (2016). "Longer Interset Rest Periods Enhance Muscle Strength and Hypertrophy in Resistance-Trained Men." J Strength Cond Res 30(7): 1805-1812.
Schoenfeld, BJ, Pope, ZK, Benik, FM, Hester, GM, Sellers, J, Nooner, JL, Schnaiter, JA, Bond-Williams, KE, Carter, AS, Ross, CL, Just, BL, Henselmans, M, and Krieger, JW. Longer interset rest periods enhance muscle strength and hypertrophy in resistance-trained men. J Strength Cond Res 30(7): 1805-1812, 2016-The purpose of this study was to investigate the effects of short rest intervals normally associated with hypertrophy-type training versus long rest intervals traditionally used in strength-type training on muscular adaptations in a cohort of young, experienced lifters. Twenty-one young resistance-trained men were randomly assigned to either a group that performed a resistance training (RT) program with 1-minute rest intervals (SHORT) or a group that employed 3-minute rest intervals (LONG). All other RT variables were held constant. The study period lasted 8 weeks with subjects performing 3 total body workouts a week comprised 3 sets of 8-12 repetition maximum (RM) of 7 different exercises per session. Testing was performed prestudy and poststudy for muscle strength (1RM bench press and back squat), muscle endurance (50% 1RM bench press to failure), and muscle thickness of the elbow flexors, triceps brachii, and quadriceps femoris by ultrasound imaging. Maximal strength was significantly greater for both 1RM squat and bench press for LONG compared to SHORT. Muscle thickness was significantly greater for LONG compared to SHORT in the anterior thigh, and a trend for greater increases was noted in the triceps brachii (p = 0.06) as well. Both groups saw significant increases in local upper body muscle endurance with no significant differences noted between groups. This study provides evidence that longer rest periods promote greater increases in muscle strength and hypertrophy in young resistance-trained men.
The above study consisted of two groups; group A rested 1 minute between sets and group B rested 3 minutes between sets. The 8-week study found that group B resting 3 minutes between sets gained both more strength and muscle thickness (size) than group A. Why did group B gain more strength and muscle than group B? Because training volume and performance are more important than fatigue.
Muscle hypertrophy is governed by total training volume.
Training Volume = Sets * Reps * Load
Resting longer between sets should allow you to complete more reps, and therefore a greater training volume, compared to less rest time. Let's look at an example of bench press volume using 225 lbs.
Lifter A (Rest 1 minute between sets)
Set 1 = 12 reps
Set 2 = 10 reps
Set 3 = 8 reps
Training Volume = 3 * 30 * 225 = 20,250 lbs
Lifter B (Rest 3 minutes between sets)
Set 1 = 12 reps
Set 2 = 11 reps
Set 3 = 10 reps
Training Volume = 3 * 33 * 225 = 22275 lbs
By resting longer between sets, Lifter B was able to complete 3 more reps than Lifter A. Lifter B's training volume was 2,025 lbs greater than Lifter A's. If you just look at one exercise, 2025 lbs may not seem like a huge difference. But think about training volume if the above was applied to multiple exercises over the course of 8 weeks... Lifter B's total training volume would be MUCH GREATER than Lifter A's. Greater volume = greater gains.
It has long been my belief that timing rest periods offers little benefit and one should perform the next set when they feel ready to maximize performance. Performing sets when feeling fatigued never made sense to me as performance would be hindered. The results of this study support my philosophy that longer rest periods allow your to perform better and lead to increased gains in strength and muscle size. My recommendation is not to time rest periods at all and simply perform the next set when you feel ready to do so.