Similar Metabolic Responses During Resistance Exercise Despite Significant Differences In Power: Effects Of Matched Work

Abstract

PURPOSE: Load and contraction intensity have both been shown to increase metabolic responses to resistance exercise, but total work is primarily responsible for resultant energy costs. Therefore, we examined whether compound sets of squats with varying loads and contraction intensities would alter metabolic responses to resistance exercise when total work was matched. Compound sets included explosive squats followed by heavy squats. METHODS: Eight healthy men (23±3 yrs; 83±22 kg; 174±7 cm) performed three protocols, one each week, designed to compare energy expenditure between four sets of squats performed with either recreational contractions (neither deliberately explosive nor slow) with 65% of 1RM (REC), compound sets with two explosive followed by eight heavy squats using 68.75% of 1RM (2/8), and four explosive followed by six very heavy using 75% (4/6). All explosive squats for 2/8 and 4/6 used 50% of 1RM. Subject’s 1RM was determined using a plate-loaded squat machine, and each protocol was randomly assigned in a counterbalanced order. In addition to the standardization of repetition speed, ROM, and rest intervals, total work performed (reps x sets x load) was identical across protocols. Expired air was collected continuously before (15 m), during (20 m), and after (30 m) each exercise protocol using a metabolic cart. Data were analyzed using a two-way repeated measures ANOVA with Fisher’s least significant difference (LSD) post hoc analyses. We hypothesized that there would be no difference in metabolic responses between 2/8 and 4/6 squats because total work was matched. RESULTS:Metabolic responses (ml·kg·min-1) were not significantly different (p≤0.05) among protocols (see Table). CONCLUSIONS: Compound sets of squats using heavier loads and more explosive contractions did not elicit greater metabolic responses despite significantly greater peak power output.