To examine the effects of different rest intervals on the repeatability of maximum strength, researchers from Tennessee asked 17 highly-trained men to repeat their 1RM (repetition maximum) in the barbell squat. The lifters performed their 1RM twice (on three separate occasions) using different rest intervals; 1 minute, 3 minutes and 5 minutes.
Barbell squats were a good choice of exercise for this study as it is an important exercise for drug-free bodybuilders. It stimulates growth in just about every muscle in the entire body. Barbell squats also trigger the secretion of large amounts of bio-active anabolic hormones into circulation such as growth hormone and testosterone.
Results showed that for the 1 minute rest interval, 13 of 17 subjects successfully completed their best 1RM in the squat a second time. For the 3 minute rest interval, 16 of 17 bodybuilders were successful. For the 5 minute rest interval, 15 of 17 were successful. Due to the low number of participants, statistical analyses were not sensitive enough to reveal any differences between these rest intervals.
However, to me these figures suggest that 3 minutes rest between working sets provided the best results (it allowed 16 of the 17 bodybuilders to replicate their best lift). The three minute rest period is about perfect for the key lifts such as squats, deadlift and bench press. Based on the results you could also say that a rest interval of 1 minute might get the job done but I wouldn’t risk it if I was performing all out sets of 4-6 reps.
Always remember, the name of the muscle-building game is to stimulate growth and this can only be achieved by placing maximum overload on the muscle. Although the research on this topic is limited, I generally believe that a rest interval of 3 minutes appears to be the most effective for key exercises such as the barbell squat and deadlift exercises as it enables maximum overload to be used in each working set.
Source: Sports Medicine, 2009.
