Non-local Muscle Fatigue in Young and Middle-Aged Women following Fast-Paced Walking.

Non-local muscle fatigue (NLMF) has been well-studied in young individuals following acute, higher intensity exercise; however, the effects of age on NLMF are unclear and limited research exist in women. Research examining age-related differences in NLMF following tasks mimicking everyday life such as fast-paced walking is needed. The purpose of this study was to determine the potential differences in NLMF for maximal and rapid force capacity between young and middle-aged women following an acute bout of fast-paced walking. Young (YW; n=16; 21±2 yrs) and post-menopausal, middle-aged (MW; n=14; 55±3 yrs) women completed a testing visit following a familiarization session. Handgrip testing was performed before and after a 6-min, fast-paced walking task. Maximal force, and early (0-100 ms) and late (0-200 ms) rapid force metrics were calculated from the force-time curve captured during handgrip testing. Rating of perceived exertion (0-10) was also obtained. Two-way mixed group × time ANOVAs were used to compare changes between groups. RPE was similar for YW (3.00±1.16) and MW (3.29±1.45) (p=0.560; d=0.22). Maximal force increased in YW (p=0.024; d=0.52) but remained unchanged in MW (p=0.092; d=0.56). Peak (p<0.001; =0.477) and early (p<0.001-p=0.002; = 0.284-0.365) rapid force decreased similarly for both groups. Late rapid force remained unchanged (p=0.210-0.688; =0.055-0.006). Despite no effect of age, NLMF was exhibited solely through early rapid force capacity following moderate intensity fast-paced walking. The divergent responses between maximal and rapid force are an important consideration for future research, given the implications for physical function in older populations.