One of the fundamental variables of weight training is the amount of rest you take between sets. For the most part, novice bodybuilders tend to try to use relatively short rest periods between sets in order to stimulate and maintain a “pump” during their workouts. After all, a pump is like instant gratification; start lifting and within 10 minutes you are bigger than you were when you walked into the gym that day. More advanced bodybuilders also tend to use shorter rest periods between sets because of trickle-down research they heard about a study that said short rest periods stimulate more anabolic hormone release during a workout.
Surely there must be more specific info we can use to decide just how long we should rest between sets to maximize our gains. And there is.
STUDY NO. 1
First, let’s discuss the notion that using short rest periods to trigger greater anabolic hormone release is key to maximizing gains. The idea that a spike in testosterone and growth hormone is responsible for triggering hypertrophy has been championed by a couple of well-known researchers for nearly three decades. Yet it wasn’t until 2009 when a group of researchers at McMaster University in Ontario, finally put the assumption to the test.(1) In their first study they compared two conditions (high-hormone spike and no-hormone spike) and their effects on post-work-out muscle protein synthesis. In the low-hormone spike condition, test subjects did 4 sets of 10 reps doing one-arm cable preacher curls with about 60–120 seconds rest between sets. In the high-hormone condition, test subjects did the same single-arm exercise but with the opposite arm, followed immediately by 5 sets of 10 reps of leg presses at ∼90% of 10 reps max (RM) and 3 sets of 12 reps of leg extension/leg curl supersets (1 set of each back-to-back) using the same rest periods to trigger a good spike in anabolic hormones. Both groups drank 25 grams of whey protein immediately following the workout. Cutting right to the chase, there was no difference at all between groups. The spike in hormones had no effect on post-workout muscle protein synthesis.
STUDY NO. 2
Later, this same group of scientists wanted to know if perhaps the benefits of triggering a spike in hormones by training large muscle groups with short rest periods only became evident after a longer training period. So they did a follow-up study using essentially the same protocol but had the subjects train for a full 15 weeks.(2) This time they measured changes in muscle mass and strength to see whether there would be a spike in hormones consistently over 15 weeks. Despite causing huge differences in circulating hormone levels during the subjects’ workouts, the scientists found no differences in the increases in strength or hypertrophy in muscle exercised under low- or high-hormone conditions by the end of the trial.
STUDY NO. 3
So what then? If using short rest periods to trigger a hormone spike doesn’t do any good, might there be some other reason to use short or long rest periods? A study published in the Journal of Strength and Conditioning Research focused on this very question.(3) This study involved a 10-week resistance training program with either 1 or 2.5 minutes of rest between sets, working out four times per week. The subjects were given a two-day split of training legs, shoulders, and abs one day, and chest, back, and arms the next. The researchers measured hormonal changes, changes in lean mass, thigh muscle mass, arm muscle mass, and the men’s 5RM before and after the study. Interestingly, the spike in testosterone and growth hormone caused by short rest periods was completely gone after five weeks of training. At that same point in time, the long-rest group displayed a less dramatic hormonal response to training but tended to experience greater increases in strength and muscle mass in the arms and legs. These results confirm previous research showing that using 2 minutes as opposed to 5 minutes rest between sets has no perceivable effect on muscle mass gains.(4)
STUDY NO. 4
Finally, in somewhat of a complicated protocol, a group out of Japan wanted to compare what they considered strength-type training with bodybuilding-type training.(5) They did a 10-week study in which the first six weeks consisted of a “hypertrophy-phase” using a high-rep/short-rest routine. That was followed by four weeks of a “strength-phase” using 5 sets using 90% 1RM and 3 minutes’ rest or a “combined-phase” using the same 5 sets with 90% 1RM but with the addition of a burnout set following a 30-second rest using only 50% 1RM. During the first phase, both groups showed equal increases in muscle mass, but during the second phase, only the group that combined heavy sets and a finishing burnout set showed continued growth for the next four weeks. What this tells us is that adding a burnout set (or dropset) following your last heavy set may lead to even greater gains. This isn’t entirely unexpected considering what we see with occlusion (aka blood-flow restricted) training. Occlusion training causes extreme metabolic stress within the muscle, and that alone can lead to significant muscle growth.
These studies provide evidence that, for the most part, and particularly for new lifters, the amount of time you take between sets really isn’t going to make a big difference in your gains. But as you get a few years under your weight belt, it is a good idea to combine both longer rest with shorter rest periods within the same workout. Use enough rest to ensure that you are able to complete the number of sets you planned with the amount of weight you are supposed to, then add either a dropset to your last heavy set, or do a traditional dropset for each muscle group you trained that workout before calling it quits. This will ensure you get both the load stress you need from the heavy weight, as well as the metabolic stress you want from the burnout sets to ensure you are getting maximum gains from your time in the gym.
References: 1) D.W. West et al., J Physiol., 587(Pt 21):5239–47, 2009. 2) D.W. West et al., J Appl Physiol., 108(1):60–7, 2010. 3) R. Buresh et al., J Strength Cond Res., 23(1):62–71, 2009. 4) J.P. Ahtiainen et al., J Strength Cond Res.,19(3):572–82, 2005. 5) K. Goto et al., J Strength Cond Res., 18(4):730–7, 2004