Beyond quantity: Muscle quality as the cornerstone for sarcopenia diagnosis and healthy aging

This letter provides a critical reflection on the article "Sex- and age-related declines in muscle mass, strength, physical performance, and muscle quality among community-dwelling older adults: A cross-sectional study" (Asano et al., 2025). The study significantly advances our understanding of age-related muscle deterioration by examining multiple domains, including muscle mass, strength, physical performance, and quality, in a large cohort of Japanese older adults. Key findings highlight that muscle strength and physical performance decline more rapidly than muscle mass, emphasizing the importance of assessing muscle quality over mass as a predictor of frailty and disability risk. Beyond the study's conclusions, we argue that muscle quality should be incorporated into universal diagnostic criteria for sarcopenia. Muscle mass alone fails to capture the complexity of muscle aging and its impact on functionality. The study further reveals that lower limbs are more vulnerable to age-related decline than upper limbs, suggesting targeted interventions for lower extremity strength and power. Additionally, it underscores sex-specific differences, with men showing faster increases in intramuscular fat and women experiencing sharper declines in morphological muscle quality after age 75. These findings support the integration of muscle quality into diagnostic criteria for sarcopenia and call for more aggressive preventive strategies for those aged 75 and older. We recommend that clinical and public health strategies prioritize muscle quality assessments and interventions tailored to sex- and limb-specific vulnerabilities, ideally initiated before the age of 75. This approach could provide a more accurate early detection of sarcopenia and significantly enhance the effectiveness of aging-related interventions.