Acute effects of different muscle fatigue conditions during strength training on localized muscle bioimpedance in women

This study aims to compare the localized muscle bioimpedance (ML-BIA) responses under different muscle fatigue conditions during strength training (ST). Twelve women participated in the study, which followed a crossover, counterbalanced, and randomized design. The experimental sessions were conducted using a 45° leg press machine, consisting of two conditions: a session until muscle failure (MF) and a session with no muscle failure (NMF). ML-BIA was assessed before the sessions, immediately after all sets were completed, and 20 and 30 min post-sessions. The ML-BIA measures of resistance (R), reactance (XC), and phase angle (PA) of the quadriceps were obtained. The countermovement Jump (CMJ) was assessed before and after both conditions. Repeated measures analysis of variance was used to compare conditions, with a significance level set at p < 0.05. In the CMJ test, significant reductions in jump height and power were observed only in the MF condition (p < 0.001). PA showed significant reductions compared to rest only in the MF condition (p < 0.001), with reductions maintained up to 30 min after the session. Our data showed that ML-BIA parameters respond differently under varying fatigue conditions, with PA decreasing only in the higher fatigue condition.