R code for "The contribution of age and sex hormones to female neuromuscular function across the adult lifespan" Publish JPhys 2025 (doi: ahead of print)
Abstract Neuromuscular ageing is characterized by neural and/or skeletal muscle degeneration that decreases maximal force and power. Female neuromuscular ageing occurs earlier in life compared to males, potentially due to sex hormone changes during the menopausal transition. We quantified neuromuscular function in 88 healthy females represented equally over each decade from 18-80 years of age and investigated the potential role of decreased ovarian hormone concentrations following menopause. Neuromuscular assessment included quadriceps maximal voluntary and evoked isometric torque and surface electromyography measurements, plus one-repetition maximum leg press. Voluntary and evoked torques and one-repetition maximum decreased non-linearly with age, with accelerated reductions starting during the fourth decade. An absence of changes in volitional recruitment of existing quadriceps motor units and Ia afferent facilitation of spinal motoneurons suggests that functional decline was largely mediated by impairment in intrinsic peripheral muscle function and/or neuromuscular transmission. Maximal muscle compound action potential amplitude decreased with increasing age for rectus femoris muscle only, indicating increased vulnerability to neuromuscular degeneration compared to vastus lateralis and medialis. In postmenopausal females, some variance in data was explained by inter-individual differences in quadriceps lean and fat tissue composition and lifestyle factors including physical activity and protein intake. Further, changes in total or free concentrations of oestradiol, progesterone and/or testosterone explained some of the variability in the data across all principal comments and were correlated with -related decreases in isometric voluntary and evoked torque responses. In conclusion, we demonstrate an accelerated onset of neuromuscular degeneration of peripheral muscular origin around menopause onset, which is associated with changes in sex hormone concentrations. Interventions aimed at mitigating declines in ovarian hormones and their subsequent effects on neuromuscular function post menopause should be further explored.