Research Square · Jul 31, 2026
Association between side-specific isokinetic quadriceps strength and low skeletal muscle mass index in community-dwelling older adults: a cross-sectional study
By Lee A, Jo YJ, Lee S et al.
Background Sarcopenia is common in older adults and predicts adverse outcomes. contemporary consensus definitions use low muscle strength as the entry point for case-finding, but confirmation requires demonstration of low muscle mass, typically quantified by dual-energy X-ray absorptiometry (DXA) or bioelectrical impedance analysis (BIA), which are not universally accessible. Quadriceps strength is functionally central to lower-limb health and can be objectively measured by isokinetic dynamometry. However, previous isokinetic studies in sarcopenia have typically assessed a single, usually dominant, limb and have not compared the left- and right-side association with muscle mass. We therefore examined side-to-side differences in isokinetic knee muscle performance and the association between side-specific quadriceps strength and low skeletal muscle mass index (low SMI) in community-dwelling older adults. Methods In this cross-sectional study, community-dwelling adults aged ≥ 60 years underwent isokinetic knee strength testing at an angular velocity of 60°/s. Peak torque, total work, and average power of the quadriceps and hamstrings were measured bilaterally, and the hamstring-to-quadriceps (H:Q) ratio was calculated. Participants were classified as normal SMI or low SMI using sex-specific Asian Working Group for Sarcopenia (AWGS) 2019 criteria. Paired t-tests compared right- and left-side variables; age- and sex-adjusted binary logistic regression and receiver operating characteristic (ROC) curve analyses evaluated the association of side-specific quadriceps variables with low SMI. Results A total of 223 participants were included in the analysis (177 normal SMI, 46 low SMI; mean age 69.88 ± 7.67 years). Right quadriceps peak torque, total work, and average power were significantly greater than the corresponding left-side values (all p < 0.001), whereas hamstring variables showed no significant side-to-side differences. In adjusted models, higher right quadriceps peak torque (odds ratios [ORs] 0.966), total work (ORs 0.992), and average power (ORs 0.952) were associated with lower odds of low SMI (all p < 0.001), whereas left-side associations were weaker. Area-under-the-curve (AUC) values were higher on the right (0.65–0.67) than on the left (0.61–0.62) but all remained below 0.70. Conclusions The association was more consistent for the stronger limb, suggesting that the absolute strength- and power-generating capacity of the quadriceps is the more relevant correlate of low SMI.