TO EXPLORE sex specific effects of stroke on motor performance, investigators studied 41 chronic stroke survivors at least six months after stroke and 23 age matched neurotypical adults. Participants completed a sustained submaximal isometric knee extension contraction at 30% of maximal voluntary strength using the paretic leg for stroke survivors and the dominant leg for controls. Task duration in seconds indexed stroke neuromuscular fatigability, with shorter duration indicating greater fatigability during isometric exercise. Potentiated quadriceps twitch responses and surface electromyography were recorded to characterize muscle contractile properties and neuromuscular activation during the fatiguing task.
Stroke survivors showed shorter task duration than neurotypical controls, confirming greater overall neuromuscular fatigability after stroke. Across all participants, males exhibited shorter task duration than females. However, a significant interaction between group and sex showed that stroke related increases in fatigability were specific to females.
Sex Differences in Stroke Neuromuscular Fatigability
Female stroke survivors demonstrated markedly shorter task duration than neurotypical females, whereas task duration was similar in male stroke survivors and neurotypical males. Among neurotypical adults, females sustained the contraction longer than males. Within the stroke group, task duration did not differ significantly between males and females, suggesting that stroke removed the usual female advantage in neuromuscular fatigability during isometric exercise.
Neuromuscular measurements supported distinct mechanisms in women and men. Stroke survivors showed smaller reductions in potentiated twitch force and smaller increases in electromyography amplitude than controls during the fatiguing contraction, consistent with altered neuromuscular activation and contractile responses. In female stroke survivors, shorter task duration correlated with less reduction in potentiated twitch, whereas in male stroke survivors shorter duration correlated with greater reduction in potentiated twitch.
Clinical Implications for Rehabilitation
These findings suggest that stroke neuromuscular fatigability may arise from different central and peripheral mechanisms in females and males. For clinicians, sex specific assessment of neuromuscular fatigability during isometric exercise may help tailor stroke rehabilitation strategies and exercise prescriptions for chronic stroke survivors. Recognizing that stroke can preferentially increase fatigability in females may prompt closer monitoring of effort, rest intervals, and task progression to optimize functional recovery and motor related outcomes over the long term.
Reference: Zhou Z et al. Stroke Increases Neuromuscular Fatigability in Females but not Males During Isometric Exercise. Med Sci Sports Exerc. 2025;doi:10.1249/MSS.0000000000003914.
