The "hypertrophy specialist" Brad Schoenfeld has published yet another fantastic study detailing not only the greater strength gains from longer interset rest periods, but the greater muscular growth adaptations too.
Abstract: 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.
Research has previously told us that greater rest periods are superior to shorter rest periods when it comes to strength and power adaptations, but there hasn't been nearly as much support and evidence suggesting the same for hypertrophy training.
The belief that shorter rest periods are ideal for training for hypertrophy purposes is challenged with research like this. Not only do we know that longer rest periods are superior for strength and power adaptations, research like this is indicating that longer rest periods illicit greater muscular growth as well. One could postulate that longer rest periods allow for greater recovery and therefore greater force and output on every subsequent set. More force and output on each set allows for greater overall training volume, which would increase the training load.
I also appreciate the fact that this study was conducted on trained individuals. Many strength and hypertrophy studies are conducted on non-trained individuals, who more often than not improve their strength and muscular size simply by being in the study alone (noob gains).
So, how practical is this for you, the reader?
Well, it would appear that rather than slugging through sets with short rest periods, you would be better off resting for longer periods and allowing your muscles to recover more in order to maximize the potential on each subsequent set.
The disadvantage to this training style includes the obvious fact that workouts could potentially take much longer if you are resting for longer periods and one of your primary goals includes getting stronger and increasing muscular size. Rather than waiting around between sets, however, you can get creative with your training and do good old fashioned circuits, training antagonistic movements. For example using an EMOM (every minute on the minute) setup, training bench press on the first minute, barbell row on the second minute, an accessory or core movement on the third minute, rest the 4th minute, and then repeat. This allows the time between exercises to be at least 3 minutes yet keeps you moving the entire time to save on overall workout length.