Influence of sex on performance fatigability of the plantar flexors following repeated maximal dynamic shortening contractions

Abstract

https://mc06.manuscriptcentral.com/apnm-pubs ABSTRACTThe purpose was to determine sex-differences in fatigability during maximal, unconstrained velocity, shortening plantar flexions. The role of time-dependent measures (i.e., rate of torque development (RTD), rate of velocity development (RVD), rate of neuromuscular activation) in such sex-related differences was also examined. By task termination, females exhibited less reductions in power and similar changes in rate of neuromuscular activation than males, indicating females were less fatigable than males.

Differential contributions of fatigue‐induced strength loss and slowing of angular velocity to power loss following repeated maximal shortening contractions

“…In the present study, the time-course changes in power and the value relative to the baseline were not always consistent with those in angular velocity and dynamic torque ( Figures 1d-f and 4) despite the fact that both the fatigue-related reductions in angular velocity and dynamic torque have been reported to impair power production (Lanning et al, 2017;Wallace et al, 2016). Briefly, power recovered faster than angular velocity and slower than dynamic torque.…”

“…However, in the current study, the participants repeated maximal effort 20%MVC isotonic dorsiflexions until peak power fell below 60% of Pre twice in a row. Therefore, as each figure in these studies shows, individual variations in power were obviously greater in the previous studies (Lanning et al, ; Wallace et al, ) than in the current study. The amount of variability of parameters affects the degree of correlation (Goodwin & Leech, ), and thus it is not surprising that the aforementioned discrepancy in the correlation coefficients between the studies.…”

“…Further studies using different loads of the fatiguing task are required to strengthen the findings of the current study. Immediately following the fatiguing task, compared with the correlation coefficients of power loss with fatigue-induced reductions in angular velocity (r = .91-.94) or dynamic torque (r = .87-.96) of previous studies (Lanning et al, 2017;Wallace et al, 2016), those of the current study (r = .255 for angular velocity and r = .456 for dynamic torque) were very low ( Figure 5). This discrepancy is likely owing to the task dependent nature of fatigue.…”

“…This discrepancy is likely owing to the task dependent nature of fatigue. In the previous studies, all participants continued the fatiguing task the same number of times (200 times in Lanning et al, 2017;50 times in Wallace et al, 2016). However, in the current study, the participants repeated maximal effort 20%MVC isotonic dorsiflexions until peak power fell below 60% of Pre twice in a row.…”

“…Fatigue can be defined as any exercise‐induced reduction in the ability to generate force or power, regardless of whether or not the task can be sustained (Gandevia, ), and can be quantified as time‐course changes in maximum voluntary contraction (MVC) torque (or force), and/or power during and following a fatiguing task (Lanning, Power, Christie, & Dalton, ; Lee et al, ; Senefeld, Pereira, Elliott, Yoon, & Hunter, ; Thompson, Conchola, & Stock, ; Wallace, Power, Rice, & Dalton, ). Optimal performance of dynamic contractions requires not only muscle force production but also a velocity component, as such, relying solely on measurements of isometric MVCs to reflect fatigue‐induced changes in neuromuscular function, may be inappropriate, especially when making inferences on fatigue‐induced changes in dynamic performance (Cheng & Rice, ; Dalton, Power, Vandervoort, & Rice, ).…”