Cross-sectional comparison of lower-limb muscle strength and contractile properties according to Parkinson's disease and sarcopenia status.

This cross-sectional study compares lower-limb isometric strength and tensiomyography-derived contractile properties between patients with Parkinson's disease and age-matched controls across sarcopenia classifications, with predefined covariate control. However, despite the clinical relevance of muscle dysfunction in Parkinson's disease and sarcopenia, TMG-derived assessments of muscle contractile properties remain limited in these populations. PD is a progressive neurodegenerative disorder marked by motor symptoms such as bradykinesia and rigidity, while sarcopenia is an age-related condition characterized by loss of muscle mass and strength. Both contribute to impaired mobility and increased fall risk, though their physiological signatures may differ. In this cross-sectional study, 60 older adults aged 58-85 years (20 with PD and 40 age-matched healthy controls; 39 males, 21 females) were assessed for isometric muscle strength across eight major lower limb movements using a handheld dynamometer, and for muscle contractile properties of four muscles-lateral gastrocnemius, medial gastrocnemius, soleus, and tibialis anterior-using tensiomyography (TMG). Compared to healthy controls, individuals with PD showed prolonged contraction time (Tc, the time between 10 and 90% of maximal contraction) and reduced maximal muscle displacement (Dm, the peak radial displacement of the muscle belly) in the lateral gastrocnemius (e.g., Tc↑: + 23.6%, Dm↓: -17.8%), suggesting neuromuscular impairment. Sarcopenic participants exhibited lower peak isometric strength in hip and knee extension tasks (e.g., -29.5% in hip extension, -26.2% in knee extension based on maximal voluntary contraction), reflecting task-specific deficits likely related to proximal muscle mass loss. While these results are based on cross-sectional data and should be interpreted cautiously, they suggest the presence of differing neuromuscular patterns in PD and sarcopenia. The findings offer preliminary insights into how PD and sarcopenia may differentially affect muscle strength and contractile characteristics, which could inform future research and clinical considerations regarding lower limb function.