Martorelli, S., Martorelli, A., Cunha, R., Pereira, M. C., Jesus, D., Rocha Jr., V., Brown, L. E., & Bottaro, M. (2012). Neuromuscular and metabolic responses to power training: Effects of different rest intervals. Presentation 1864 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

This study compared the effects of three different rest intervals on mean power output, blood lactate concentration, and electromyography in trained men (N = 14). Ss performed six sets of six repetitions of squat exercise at 60% of 1 RM on a Smith machine. Each S performed three different rest-interval protocols (1, 2, and 3 minutes) on three different days in counterbalanced order, separated by at least 72 hours. Mean power output was measured every set using a velocity transducer. Blood lactate concentration and vastus medialis EMG (maximum isometric voluntary contractions) were measured before and after the six sets in each rest interval.

There were no significant differences between the rest-interval protocols on mean power output. However, the 1-minute rest-interval protocol showed a significant reduction in power output from the first to sixth set. In contrast, no significant reduction was observed between the first and sixth sets for 2- or 3-minute rest-interval protocols. Blood lactate was significant greater after the 1-minute rest interval when compared to the 2- and 3-minute rest intervals. Only the 3-minute rest interval presented a significant reduction in root mean square values of the vastus medialis maximum isometric voluntary contractions (EMG).

Implication. One-minute rest intervals showed greater decline in muscular performance and greater levels of fatigue metabolic by-products in a power training experience. After three minute rest intervals, muscle activation was less at the end of the training session.

If an individual wants to maintain power output with less fatigue and greater muscle activation during power training, two-minute rest intervals should be used.

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