Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, UK.
Clinical, Metabolic and Molecular Physiology, MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK.
J Physiol. 2021 Jan;599(1):193-205. doi: 10.1113/JP280679. Epub 2020 Oct 22.
Masters athletes maintain high levels of activity into older age and allow an examination of the effects of aging dissociated from the effects of increased sedentary behaviour. Evidence suggests masters athletes are more successful at motor unit remodelling, the reinnervation of denervated fibres acting to preserve muscle fibre number, but little data are available in females. Here we used intramuscular electromyography to demonstrate that motor units sampled from the tibialis anterior show indications of remodelling from middle into older age and which does not differ between males and females. The age-related trajectory of motor unit discharge characteristic differs according to sex, with female athletes progressing to a slower firing pattern that was not observed in males. Our findings indicate motor unit remodelling from middle to older age occurs to a similar extent in male and female athletes, with discharge rates progressively slowing in females only.
Motor unit (MU) remodelling acts to minimise loss of muscle fibres following denervation in older age, which may be more successful in masters athletes. Evidence suggests performance and neuromuscular function decline with age in this population, although the majority of studies have focused on males, with little available data on female athletes. Functional assessments of strength, balance and motor control were performed in 30 masters athletes (16 male) aged 44-83 years. Intramuscular needle electrodes were used to sample individual motor unit potentials (MUPs) and near-fibre MUPs in the tibialis anterior (TA) during isometric contractions at 25% maximum voluntary contraction, and used to determine discharge characteristics (firing rate, variability) and biomarkers of peripheral MU remodelling (MUP size, complexity, stability). Multilevel mixed-effects linear regression models examined effects of age and sex. All aspects of neuromuscular function deteriorated with age (P < 0.05) with no age × sex interactions, although males were stronger (P < 0.001). Indicators of MU remodelling also progressively increased with age to a similar extent in both sexes (P < 0.05), whilst MU firing rate progressively decreased with age in females (p = 0.029), with a non-significant increase in males (p = 0.092). Masters athletes exhibit age-related declines in neuromuscular function that are largely equal across males and females. Notably, they also display features of MU remodelling with advancing age, probably acting to reduce muscle fibre loss. The age trajectory of MU firing rate assessed at a single contraction level differed between sexes, which may reflect a greater tendency for females to develop a slower muscle phenotype.
大师级运动员在老年时保持高水平的活动，并允许将衰老的影响与久坐行为的影响分开进行检查。有证据表明，大师级运动员在运动单位重塑方面更为成功，即去神经纤维的再支配作用可保留肌肉纤维数量，但女性的数据很少。在这里，我们使用肌内肌电图证明，从胫骨前肌采集的运动单位显示出从中年到老年重塑的迹象，并且男女之间没有差异。运动单位放电特征的与年龄相关的轨迹因性别而异，女性运动员进展为较慢的放电模式，而男性则没有观察到这种模式。我们的研究结果表明，从中年到老年，男女运动员的运动单位重塑程度相似，只有女性的放电率逐渐减慢。
运动单位（MU）重塑可最大程度地减少老年失神经后肌肉纤维的丢失，这在大师级运动员中可能更为成功。有证据表明，该人群的运动表现和神经肌肉功能会随着年龄的增长而下降，尽管大多数研究都集中在男性上，而女性运动员的数据很少。对 30 名年龄在 44-83 岁的大师级运动员（16 名男性）进行了力量、平衡和运动控制的功能性评估。使用肌内针电极在胫骨前肌（TA）的等长收缩下，以 25%最大随意收缩的方式采集单个运动单位电位（MUP）和近纤维 MUP，并用于确定放电特征（放电率、变异性）和周围 MU 重塑的生物标志物（MUP 大小、复杂性、稳定性）。多水平混合效应线性回归模型检查了年龄和性别的影响。所有神经肌肉功能方面都随着年龄的增长而恶化（P<0.05），没有年龄与性别之间的相互作用，尽管男性更强壮（P<0.001）。MU 重塑的指标也随着年龄的增长而以相似的程度逐渐增加，在两性中都是如此（P<0.05），而女性的 MU 放电率随着年龄的增长而逐渐降低（p=0.029），男性则呈非显著性增加（p=0.092）。大师级运动员表现出与年龄相关的神经肌肉功能下降，在男性和女性中基本相同。值得注意的是，他们随着年龄的增长也表现出 MU 重塑的特征，可能有助于减少肌肉纤维的丢失。在单次收缩水平上评估的 MU 放电率的年龄轨迹在性别之间存在差异，这可能反映出女性更容易发展出较慢的肌肉表型。
