Less Rest for Size, More Rest for Strength?
The advice regarding inter-set rest periods has long been that rest and intensity are inversely related. In other words, if you did a lighter weight, higher-rep set, you rested for anywhere from 45 seconds to a minute. If you did a lower-rep heavy set, you rested for 2 or more minutes.
By following this time formula, you either grew muscle (through the higher rep, shorter rest periods) or you built strength (through the lower rep, higher intensity sets). You'd choose to develop one or the other and never the twain shall meet.
It was almost like a Chinese menu that offered food from column A or food from column B, but with no substitutions. But what if you want some spicy Kung Pao size with a little bit of tangy Moo Goo Gai Pan strength on the side?
You can have both, says T Nation contributor and sports scientist Brad Schoenfeld. He and his colleagues conducted a study that shows you can build both size and strength by taking 2-minute rest periods between sets.
Onesies and Twosies
Schoenfeld and his cronies recruited 24 experienced male lifters and divided them into two groups. Both groups did the same program, but one group rested for 1 minute between sets and the other group rested for 2 minutes between sets.
After 8 weeks, the 2-minute group increased their 1RM in the squat and bench press more than the 1-minute group. Surprisingly, the 2-minute group also gained more muscle in their biceps, triceps, and anterior quads than the 1-minute group.
Schoenfeld, like most PhDs, is uncomfortable making definitive statements about something based on the results of only one study, lest he be proven wrong some day and be punished by having to walk naked down the halls of academia while other PhDs scold him with cries of "Shame! Shame!"
That's why he was quick to point out that these results don't "necessarily hold true when other training variables are manipulated." He also cautioned that the 2-minute rest intervals would double the length of workouts, which of course might be problematic for those rare lifters who reportedly have lives outside the gym.
Whether the 2-minute rest periods actually lead to more strength and muscle will need further study, but you don't have to wait for the results; just try it yourself for a few weeks.
As far as the workouts being longer, you could ameliorate the problem by using the 2-minute rest periods to work ancillary muscle groups that might normally be worked later on, or near the end of a training session. For instance, you could do sets of biceps curls, calf raises, or ab work while recovering from sets of squats, bench presses, or deadlifts.
Schoenfeld, Brad J. et al. "Longer Interset Rest Periods Enhance Muscle Strength and Hypertrophy in Resistance-Trained Men." Journal of Strength & Conditioning Research: July 2016 - Volume 30 - Issue 7 - p 1805–1812.