Investigation of age- and sex-specific reference values for lower-limb muscle thickness using ultrasonography

Objective: The aim of this study was to establish age- and sex-specific reference values for lower limb muscle thickness using ultrasonography, and to examine their association with physical performance in community-dwelling adults. Patients/Materials and Methods: This prospective observational study was conducted involving 666 community-dwelling adults (296 men and 370 women) aged 18 years and older in Akita and Aichi Prefectures, Japan. The thickness of the medial gastrocnemius (MG) was measured using ultrasonography. Results: In men, MG thickness peaked in their 40s, followed by those in their 20s and 30s. Among women, a peak was observed in those in their 30s, followed by those in their 20s. Both sexes showed a consistent downward trend in muscle thickness following their respective peaks. Notably, participants aged 80 years and older exhibited the lowest values across all age groups, indicating a significant age-related decline. Conclusion: This study clarified the age-related trajectory of lower limb muscle thickness across a broad population from adulthood to old age. These findings suggest that ultrasonographic measurement is a sensitive and effective indicator of the age-related skeletal muscle loss associated with aging.