No Influence of Rest Between Sets on Creatine Kinase and Lactate Levels

Probably, you would assume that the reduction of rest in between sets from 3 minutes to 60 seconds would have an effect if not on creatine kinase, then at least on lactate levels. A recent study published in The Journal of Strength and Conditioning Research refutes this common-sense assumption (Machado. 2010):

Each session consisted of 4 sets of 10 repetitions with 10 repetition maximum loads for the chest press, pullover, biceps curl, triceps extension, leg extension, and prone leg curl. The sessions differed only in the length of the rest interval between sets and exercises, specifically: 60, 90, 120, 180 seconds. Serum CK and LDH were significantly (p < 0.05) elevated 24-72 hours after each session, with no significant differences between rest intervals (p = 0.94 and p = 0.99, respectively). The mechanical stress imposed by the 4 resistance exercise sessions invoked similar damage to the muscle fibers independent of the rest interval between sets.

Since the exact relation between markers of muscle damage, hypertrophy and strength gains have yet to be established, it is as of yet impossible to derive concrete training advice from these findings. In other words, this does not mean that resting times do not make a difference in view of the eventual training results. Shorter rest periods, for example have been associated with increased growth hormone response and an overall more pronounced anabolic stimulus.