Purpose: The neuromuscular mechanisms leading to impaired motor performance in the presence of mental fatigue remain unclear. It is also unknown if mental fatigue differentially impacts motor performance in males and females. The purpose of this study was to assess the impact of mental fatigue on force production and motor unit (MU) firing behavior in males and females.

Methods: Nineteen participants performed 10-s isometric dorsiflexion (DF) contractions at 20 and 50% maximum voluntary contraction (MVC) before, during, and after completing 22 min of the psychomotor vigilance task (PVT), to induce mental fatigue. The DF force and indwelling MU firing behavior of the tibialis anterior (TA) was measured before and immediately following the PVT and within the first and final minutes of the PVT.

Results: Force steadiness and motor unit firing rate (MUFR) variability did not change during or following the PVT at either contraction intensity (p ≥ 0.16). Overall, females had more variability than males in MUFR during the 20% MVCs (15.98 ± 2.19 vs. 13.64 ± 2.19%, p = 0.03), though no sex differences were identified during the 50% MVCs (p = 0.20). Mean MUFR decreased following mental fatigue in both sexes in the 20% MVC condition (14.79 ± 3.20 vs. 12.92 ± 2.53 Hz, p = 0.02), but only in males during the 50% MVC condition (18.65 ± 5.21 vs. 15.03 ± 2.60 Hz, p = 0.01).

Conclusions: These results suggest possible sex and contraction intensity-specific neuromuscular changes in the presence of mental fatigue.

目的：尚存在精神疲劳时，导致运动功能受损的神经肌肉机制尚不清楚。精神疲劳是否对男性和女性的运动表现产生不同的影响也是未知的。这项研究的目的是评估精神疲劳对男性和女性的力量产生和运动单位（MU）射击行为的影响。

方法：19名参与者在完成22分钟的心理运动警惕任务（PVT）之前，之中和之后，分别以20％和50％最大自愿收缩（MVC）进行了10-s等距背屈（DF）收缩，以引起精神疲劳。在PVT之前和之后以及在PVT的第一分钟和最后一分钟内，测量胫骨前（DF）的DF力和留置MU的动作。

结果：在PVT期间或之后，无论哪种收缩强度，力的稳定性和运动单位的发动率（MUFR）的变化都没有改变（p≥0.16）。总体而言，在20％的MVC期间，女性的MUFR变异性大于男性（15.98±2.19 vs. 13.64±2.19％，p = 0.03），尽管在50％的MVC期间未发现性别差异（p= 0.20）。在20％MVC的情况下，男女精神疲劳后的平均MUFR降低（14.79±3.20 vs. 12.92±2.53 Hz，p = 0.02），但仅在50％MVC状态下的男性中（18.65±5.21 vs. 15.03±2.60 Hz， p = 0.01）。

结论：这些结果表明，在存在精神疲劳的情况下，可能发生的性别和收缩强度特定的神经肌肉变化。