Association of trunk and lower limb muscle thickness with sedentary behavior in patients with chronic post-stroke hemiplegia.

[Purpose] Individuals with chronic stroke often exhibit low physical activity and prolonged sedentary behavior, possibly due to muscle weakness and impaired postural control. This study investigated associations between trunk and lower limb muscle thickness and physical activity, including sedentary behavior, in ambulatory individuals with chronic post-stroke hemiplegia. [Participants and Methods] Twenty-six ambulatory individuals with chronic post-stroke hemiplegia were included. Physical activity was assessed for 7 consecutive days using a triaxial accelerometer and categorized as sedentary behavior, light physical activity, and moderate to vigorous physical activity. Bilateral muscle thickness of the diaphragm, internal oblique, gluteus medius, quadriceps, soleus, and tibialis anterior was measured using ultrasonography. Pearson's correlation and multiple regression analyses adjusted for age and Fugl-Meyer Assessment for the Lower Extremity (FMA-LE) scores were performed. [Results] Sedentary behavior was negatively correlated with the muscle thickness of the unaffected-side diaphragm, affected-side internal oblique, and unaffected-side internal oblique. Post-hoc power analysis demonstrated 0.54 statistical power. However, these associations were not independently significant after adjustment for age and FMA-LE scores. [Conclusions] Greater trunk muscle thickness was associated with less sedentary behavior in univariate analysis but not after adjustment. The independent clinical significance of trunk muscle morphology requires confirmation in larger longitudinal studies.