Jay Cutler has trained with short rest periods for years, and the same goes for Phil Heath. Watching Heath train, you’ll see he takes very short rest periods as he moves between exercises. Current research in the July issue of Journal of Strength and Conditioning Research reports that a hypertrophy protocol with rest periods consisting of 60 and 90 seconds—between thee sets of 10 reps at 70% of a one-rep max (1RM)—resulted in significant enhancements in testosterone during and immediately after exercise. The researchers also tested a strength protocol consisting of eight sets for three repetitions using 85% of a 1RM with the exact same rest periods (60 and 90 seconds). They found that even though the strength protocol used fewer repetitions and heavier weight, when the strength group kept their rest periods short between sets, they also experienced significant increases in testosterone. The moral of the story is that just because you are training heavier, this does not give you reason to rest longer.
The researchers suggested that using 60- to 90-second rest periods while strength training can lead to increases in testosterone and to greater increases in size and strength over a longer period of time.