本研究旨在表征运动引起的神经肌肉疲劳的病因及其对力量-持续时间关系的影响，以提供机械性洞察早期乳腺癌患者运动能力降低的原因。15名早期乳腺癌患者和15名健康女性进行了60次最大自主等长四头肌等长缩短肌肉收缩（MVC，3 s收缩，2 s放松）。关键力量被确定为最后六次收缩的平均力量，而W'被计算为危急力量以上产生的力量冲动。股四头肌在运动中的激活是从外展肌、内收肌和股直肌的肌电图中估计的。通过超最大电刺激引起的四头肌自愿激活（ΔVA）和四头肌抽搐力量（ΔQTw）的变化量来量化中枢疲劳和外周疲劳。 早期乳腺癌患者的MVC先于锻炼之前低于对照组（-15％，P = 0.022），这种降低在进行60次MVC的过程中持续存在（-21％，P = 0.002）。患者的绝对关键力量比对照组低（144±29N vs. 201±47N，P < 0.001 ），而W'相似（P = 0.546），结果导致总工作量降低（-23％，P = 0.001）。这与患者外展肌（P < 0.001）、内收肌（P = 0.003）和股直肌（P = 0.003）的肌肉激活程度降低有关。锻炼后，ΔVA在患者中的降低程度大于对照组（-21.6±13.3％ vs. -12.6±7.7％，P = 0.040），而ΔQTw相似（-60.2±13.2％ vs. -52.8±19.4％，P = 0.196）。 这些发现支持中枢疲劳作为化疗后早期乳腺癌患者运动能力降低的主要原因。编号 NCT04639609-2020年11月20日。 © 2023。作者（们）。

The present study aimed to characterize the etiology of exercise-induced neuromuscular fatigue and its consequences on the force-duration relationship to provide mechanistic insights into the reduced exercise capacity characterizing early-stage breast cancer patients.Fifteen early-stage breast cancer patients and fifteen healthy women performed 60 maximal voluntary isometric quadriceps contractions (MVCs, 3 s of contraction, 2 s of relaxation). The critical force was determined as the mean force of the last six contractions, while W' was calculated as the force impulse generated above the critical force. Quadriceps muscle activation during exercise was estimated from vastus lateralis, vastus medialis and rectus femoris EMG. Central and peripheral fatigue were quantified via changes in pre- to postexercise quadriceps voluntary activation (ΔVA) and quadriceps twitch force (ΔQTw) evoked by supramaximal electrical stimulation, respectively.Early-stage breast cancer patients demonstrated lower MVC than controls preexercise (- 15%, P = 0.022), and this reduction persisted throughout the 60-MVC exercise (- 21%, P = 0.002). The absolute critical force was lower in patients than in controls (144 ± 29N vs. 201 ± 47N, respectively, P < 0.001), while W' was similar (P = 0.546), resulting in lower total work done (- 23%, P = 0.001). This was associated with lower muscle activation in the vastus lateralis (P < 0.001), vastus medialis (P = 0.003) and rectus femoris (P = 0.003) in patients. Immediately following exercise, ΔVA showed a greater reduction in patients compared to controls (- 21.6 ± 13.3% vs. - 12.6 ± 7.7%, P = 0.040), while ΔQTw was similar (- 60.2 ± 13.2% vs. - 52.8 ± 19.4%, P = 0.196).These findings support central fatigue as a primary cause of the reduction in exercise capacity characterizing early-stage breast cancer patients treated with chemotherapy.No. NCT04639609-November 20, 2020.© 2023. The Author(s).