PURPOSE: The purpose of this study was to determine whether supraspinal mechanisms contribute to the sex difference in fatigability during and recovery from a dynamic and isometric fatiguing task with the knee extensors. METHODS: Transcranial magnetic stimulation and electrical stimulation were used to determine voluntary activation and contractile properties of the knee extensors in 14 men and 17 women (20.8 ± 1.9 yr) after a 1) 60-s sustained, maximal voluntary isometric contraction (MVIC), and 2) dynamic fatiguing task involving 120 maximal voluntary concentric contractions with a 20% MVIC load. RESULTS: There were no differences between men and women in the reduction of maximal torque during the sustained MVIC (54.4% ± 18.9% vs 55.9% ± 11.2%, P = 0.49) or in the decrease in power during the dynamic fatiguing task (14.7% ± 20.1% vs 14.2% ± 18.5%, P = 0.92). However, MVIC torque recovered more quickly for women than men after the sustained MVIC and the dynamic task (P < 0.05). The transcranial magnetic stimulation-elicited superimposed twitch was larger for men than for women during the sustained MVIC and in recovery (immediately post, R0.1: 4.7% ± 3.3% vs 2.4% ± 1.9% MVIC; P = 0.02), with no sex difference after the dynamic task (P = 0.35). The reduction in resting twitch amplitude was larger for men than for women immediately after the dynamic task (37% ± 22% vs 23% ± 18%; P = 0.016) with no sex difference after the sustained MVIC (64% ± 16% vs 67% ± 11%; P = 0.46). CONCLUSIONS: Supraspinal fatigue contributed to fatigability of the knee extensors more for men than for women after a maximal isometric task, whereas contractile mechanisms explained the sex difference in torque recovery after the fast-velocity dynamic task. The mechanisms for the sex difference in fatigability are task dependent.
PURPOSE: The purpose of this study was to determine whether supraspinal mechanisms contribute to the sex difference in fatigability during and recovery from a dynamic and isometric fatiguing task with the knee extensors. METHODS: Transcranial magnetic stimulation and electrical stimulation were used to determine voluntary activation and contractile properties of the knee extensors in 14 men and 17 women (20.8 ± 1.9 yr) after a 1) 60-s sustained, maximal voluntary isometric contraction (MVIC), and 2) dynamic fatiguing task involving 120 maximal voluntary concentric contractions with a 20% MVIC load. RESULTS: There were no differences between men and women in the reduction of maximal torque during the sustained MVIC (54.4% ± 18.9% vs 55.9% ± 11.2%, P = 0.49) or in the decrease in power during the dynamic fatiguing task (14.7% ± 20.1% vs 14.2% ± 18.5%, P = 0.92). However, MVIC torque recovered more quickly for women than men after the sustained MVIC and the dynamic task (P < 0.05). The transcranial magnetic stimulation-elicited superimposed twitch was larger for men than for women during the sustained MVIC and in recovery (immediately post, R0.1: 4.7% ± 3.3% vs 2.4% ± 1.9% MVIC; P = 0.02), with no sex difference after the dynamic task (P = 0.35). The reduction in resting twitch amplitude was larger for men than for women immediately after the dynamic task (37% ± 22% vs 23% ± 18%; P = 0.016) with no sex difference after the sustained MVIC (64% ± 16% vs 67% ± 11%; P = 0.46). CONCLUSIONS:Supraspinal fatigue contributed to fatigability of the knee extensors more for men than for women after a maximal isometric task, whereas contractile mechanisms explained the sex difference in torque recovery after the fast-velocity dynamic task. The mechanisms for the sex difference in fatigability are task dependent.
Authors: Andrew M Alexander; Shane M Hammer; Kaylin D Didier; Lillie M Huckaby; Thomas J Barstow Journal: Appl Physiol Nutr Metab Date: 2022-01-12 Impact factor: 2.665
Authors: Phuong L Ha; Benjamin E Dalton; Michaela G Alesi; Tyler M Smith; Trisha A VanDusseldorp; Yuri Feito; Garrett M Hester Journal: Physiol Rep Date: 2021-05