Effects of short inter-repetition rest periods on power output losses during the half squat exercise

BACKGROUND: Cluster training is being increasingly used to develop muscular power. OBJECTIVE: To determine the effects of short inter-repetition rest(IRR) periods on the capacity to maintain maximal levels of power output. METHODS: In a first session, 16 active-duty soldiers performed a progressive loading test to establish the load linked to maximal power(optimal load, OL), and the half squat 1-repetition maximum. In Session 2, six individual sets of repetitions performed to failure (or a maximum of 20 repetitions) were conducted using the loads OL, low (LL, 15% below OL), and high (HL, 15% above OL) as quickly as possible. For each load, participants performed one set without rest between repetitions (CR, continuous repetition protocol), and another set with 6 s of rest between repetitions (IRR protocol). RESULTS: The number of repetitions participants performed before exceeding a power loss threshold of 15% were higher in the IRR versus the CR protocol by 218% (11 vs. 35), 86% (7 vs. 13), and 175% (4 vs. 11) for LL, OL, and HL, respectively. CONCLUSIONS: A 6 s interval between repetitions is sufficient to induce partial recovery in participants, and could therefore improve muscle power output.