Postural stability and muscle function responses to acute brisk walking in young and middle-aged women

Age-related research on postural stability and muscle function responses following fatiguing tasks representative of everyday life is limited to older adults, despite the high prevalence of injurious falls in middle-aged women. This study sought to determine the acute effects of fast-paced walking on postural stability and rapid and maximal torque production of the plantar flexors in young and middle-aged women. Thirty-one young ( n = 16, [21 ± 2] yrs) and postmenopausal middle-aged ( n = 15, [55 ± 3] yrs) women completed a fast-paced, 6-minute (min) walking task. Before and after the task, a 30-second (s) dynamic balance test and rapid, maximal isometric contractions of the plantar flexors were completed. Indices of overall, sagittal, and frontal postural stability were derived from the balance test. Peak torque was determined, and the rate of torque development was calculated at its peak, early (0-100 ms), and later (200 ms) time intervals for isometric contractions. Two-way mixed analyses of variance with Bonferroni corrected pairwise comparisons were used for analysis. Sagittal stability was reduced more in young ( p < 0.001; d = 1.98; –47%) compared to middle-aged ( p = 0.002; d = 1.00; –41%) while all other postural stability outcomes were reduced similarly between age groups ( p < 0.001-0.002; = 0.294-0.695). Torque outcomes remained unchanged for both groups ( p = 0.085-0.989; = 0.000-0.099). Middle-aged women demonstrate similar reductions in dynamic postural stability compared to young women following a bout of fast-paced walking. Plantar flexor strength was unaffected, though this finding was likely limited by the delayed post-testing. These findings complement prospective reports regarding the susceptibility of middle-aged women to falls during brief bouts of walking.