Association between feasible muscle specific strength and sarcopenia outcomes in community dwelling Japanese older people

Muscle-specific strength (MSS) is one of the components of sarcopenia; however, its specific definition has not yet been established. This study aims to explore associations between potential and feasible indicators of MSS and history of falls as a sarcopenia outcome. We included individuals aged 65 years and older who were ambulatory who attended a Senior Citizen Community Center between August and September 2023. 128 participants gave written informed consent for this study. MSS was defined in three patterns: handgrip strength/total muscle mass (H/M), handgrip strength/dominant unilateral upper limb muscle mass (H/U), and handgrip strength/calf circumference (H/C). Multiple linear and logistic regression analyses were performed, using handgrip strength, total and dominant unilateral upper limb muscle mass, calf circumference, and three patterns of MSS as predictors. Outcomes included five repetitions for the sit-to-stand (5ST) test and history of falls within the past year. Age, sex, comorbidities were adjusted for in each analysis. MSS-H/C was associated to 5ST and history of falls (β = − 2.69, 95% CI [− 5.13 to − 0.25], p = 0.03. OR = 0.01, 95% CI [0.0002 to 0.51], p = 0.02). MSS-H/M was also associated to 5ST and history of falls (β = − 3.73, 95% CI [− 6.82 to − 0.64], p = 0.02. OR = 0.004, 95% CI [0.00004 to 0.62], p = 0.02), while handgrip strength alone was only associated to history of fall (OR = 0.86, 95% CI [0.77 to 0.96], p < 0.01). MSS-H/C and MSS-H/M combined with handgrip strength and calf circumference or total muscle mass may be more useful in defining feasible MSS related to sarcopenia outcomes than handgrip strength alone.