PDF(Pubmed)
Abstract：
Emerging questions in neuromuscular physiology revolve around whether males and females share similar neural control in diverse tasks across a broad range of intensities. In order to explore these features, high-density electromyography was used to record the myoelectrical activity of biceps brachii during trapezoidal isometric contractions at 35% and 70% of maximal voluntary force (MVF) on 11 male and 13 female participants. Identified motor units were then classified as lower-threshold (recruited at ≤30%MVF) and higher-threshold (recruited at >30%MVF). The discharge rate, interspike interval variability, recruitment and derecruitment thresholds, and estimates of neural drive to motor neurons were assessed. Female lower-threshold motor units showed higher neural drive (P < 0.001), accompanied by higher discharge rate at recruitment (P = 0.006), plateau (P = 0.001) and derecruitment (P = 0.001). On the other hand, male higher-threshold motor units showed greater neural drive (P = 0.04), accompanied by higher discharge rate at recruitment (P = 0.005), plateau (P = 0.04) and derecruitment (P = 0.01). Motor unit discharge rate normalised by the recruitment threshold was significantly higher in female lower-threshold motor units (P < 0.001), while no differences were observed in higher-threshold motor units. Recruitment and derecruitment thresholds are higher in males across all intensities (P < 0.01). However, males and females have similar activation and deactivation strategies, as evidenced by similar recruitment-to-derecruitment ratios (P > 0.05). This study encompasses a broad intensity range to analyse motor unit sex-related differences, highlighting higher neural drive and discharge rates in female lower-threshold motor units, elevated recruitment and derecruitment thresholds in males, and convergences in activation and deactivation strategies. HIGHLIGHTS: What is the central question of the study? Do male and female motor units behave similarly in low- and high-intensity contractions? What is the main finding and its importance? Female motor units show higher discharge rates in low-intensity tasks and lower discharge rates in high-intensity tasks, with no differences in recruitment behaviour. A broader inter-spike interval variability was also observed in females. These findings underline that there are sex-specific differences concern the firing strategies based on task intensity.
摘要：
神经肌肉生理学中的新兴问题围绕着男性和女性在各种强度的不同任务中是否具有相似的神经控制。为了探索这些特征，使用高密度肌电图记录11例男性和13例女性参与者在梯形等轴测收缩时的肱二头肌肌电活动,分别为最大自愿力(MVF)的35%和70%.然后将确定的运动单位分类为较低阈值（在≤30％MVF时招募）和较高阈值（在>30％MVF时招募）。放电率，尖峰间间隔变异性，招募和退伍门槛，并评估了神经驱动运动神经元的估计值。女性低阈值运动单位表现出更高的神经驱动（P<0.001），伴随着招募时更高的出院率(P=0.006)，高原（P=0.001）和退伍（P=0.001）。另一方面,男性较高阈值的运动单位表现出更大的神经驱动（P=0.04），伴随着招募时更高的出院率(P=0.005)，高原(P=0.04)和退伍(P=0.01)。由招募阈值归一化的运动单位放电率在女性低阈值运动单位中显着更高（P<0.001），而在较高阈值的运动单位中没有观察到差异。在所有强度下，男性的招募和退招募阈值均较高（P<0.01）。然而,男性和女性有相似的激活和去激活策略，相似的招募与退伍比率证明了这一点（P>0.05）。这项研究包括一个广泛的强度范围来分析运动单位性别相关的差异，突出女性低阈值运动单位中更高的神经驱动和放电率，男性招募和退伍门槛提高，以及激活和去激活策略的趋同。重点：研究的中心问题是什么？男性和女性运动单位在低强度和高强度收缩中的行为是否相似？主要发现及其重要性是什么？女性运动单位在低强度任务中显示出较高的放电率，在高强度任务中显示出较低的放电率，招聘行为没有差异。在女性中也观察到更广泛的穗间间隔变异性。这些发现强调了基于任务强度的射击策略存在性别差异。
