Mean power and surface mechanomyographic responses following fatiguing isotonic muscle actions are unaffected by ischemic preconditioning.

Abstract

Objective.The use of ischemic preconditioning (IPC) may delay the onset of fatigue, however, its impact on mean power (MP) and neuromuscular function remains unclear. The purpose of this investigation was to examine the impact of IPC prior to an acute bout of fatiguing resistance exercise on MP, surface mechanomyography amplitude (sMMG_AMP), and sMMG MP frequency (sMMG_MPF).Approach.Nineteen males randomly completed IPC on separate visits at a low (20 mmHg), moderate individualized (80% of total arterial occlusion pressure), and a supra-systolic absolute (220 mmHg) pressure. Following IPC, participants performed one-set to failure of unilateral (i.e. one leg), isotonic (i.e. constant load), concentric-only leg extensions with a submaximal load (i.e. 30% of one-repetition maximum). MP, sMMG_AMP, and sMMG_MPFwere assessed from concentric peak torque muscle actions performed at an angular velocity of 90°·s^-1prior to and immediately following the bout of exercise. Each dependent variable was analyzed with Bayesian multilevel models (i.e. random intercepts and slopes) and the fixed effects are reported as the mean difference (Mean_diff) and the 95% high-density interval (95% HDI).Main Results.There were no significant interactions or main effects of Condition for any of the dependent variables. Following the one-set to failure, however, MP (Mean_diff= 68.60 ± 1.67 W; 95% HDI: 53.80-83.60), sMMG_AMP(Mean_diff= 0.58 ± 0.04 m·s^-2; 95% HDI: 0.26-0.91), and sMMG_MPF(Mean_diff= 1.35 ± 0.13 Hz; 95% HDI: 0.32-2.39) decreased.Significance.The use of IPC prior to an acute bout of fatiguing resistance exercise did not attenuate the fatigue-induced decreases in MP, sMMG_AMP, or sMMG_MPF. These responses may be attributed to the accumulation of metabolic byproducts, decreases in muscular compliance, and/or alterations in the global firing rate of the unfused activated motor units.