Long-term exercise training has been considered as an effective strategy to counteract age-related hormonal declines and minimise muscle atrophy. However, human data relating circulating hormone levels with motor nerve function are scant. The aims of the study were to explore associations between circulating sex hormone levels and motor unit (MU) characteristics in older men, including masters athletes competing in endurance and power events. Forty-three older men (mean ± SD age: 69.9 ± 4.6 years) were studied based on competitive status. The serum concentrations of dehydroepiandrosterone (DHEA), total testosterone (T) and estradiol were quantified using liquid chromatography mass spectrometry. Intramuscular electromyographic signals were recorded from vastus lateralis (VL) during 25% of maximum voluntary isometric contractions and processed to extract MU firing rate (FR), and motor unit potential (MUP) features. After adjusting for athletic status, MU FR was positively associated with DHEA levels (p = 0.019). Higher testosterone and estradiol were associated with lower MUP complexity; these relationships remained significant after adjusting for athletic status (p = 0.006 and p = 0.019, respectively). Circulating DHEA was positively associated with MU firing rate in these older men. Higher testosterone levels were associated with reduced MUP complexity, indicating reduced electrophysiological temporal dispersion, which is related to decreased differences in conduction times along axonal branches and/or MU fibres. Although evident in males only, this work highlights the potential of hormone administration as a therapeutic interventional strategy specifically targeting human motor units in older age.

长期运动训练被认为是对抗与年龄相关的荷尔蒙下降和尽量减少肌肉萎缩的有效策略。然而，有关循环激素水平与运动神经功能的人体数据很少。该研究的目的是探索老年男性循环性激素水平与运动单位（MU）特征之间的关联，其中包括参加耐力和力量项目的大师级运动员。根据竞争状况对 43 名老年男性（平均±标准差年龄：69.9±4.6 岁）进行了研究。使用液相色谱质谱法对脱氢表雄酮（DHEA）、总睾酮（T）和雌二醇的血清浓度进行定量。在最大自主等长收缩的 25% 期间记录股外侧肌 (VL) 的肌内肌电信号，并进行处理以提取 MU 放电率 (FR) 和运动单位电位 (MUP) 特征。调整运动状态后，MU FR 与 DHEA 水平呈正相关 ( p = 0.019)。较高的睾酮和雌二醇与较低的 MUP 复杂性相关；在调整运动状态后，这些关系仍然显着（分别为p = 0.006 和p = 0.019）。在这些老年男性中，循环 DHEA 与 MU 放电率呈正相关。较高的睾酮水平与降低的 MUP 复杂性相关，表明电生理时间分散减少，这与轴突分支和/或 MU 纤维传导时间差异的减少有关。尽管仅在男性中很明显，但这项工作强调了激素管理作为专门针对老年人运动单位的治疗干预策略的潜力。