Unraveling functional decline: the relationship between muscle strength and ultrasound evaluation of biceps brachii thickness

Abstract

Skeletal muscle characteristics play a crucial role in understanding physical capacity, overall health, and outcomes. Muscle strength and muscle mass are key indicators of muscular function and sarcopenia. While previous research has explored biceps brachii muscle characteristics in isolation, there is a notable gap in comprehensive studies examining the direct correlation between biceps brachii muscle thickness (BMT), as measured by ultrasound, and muscle strength. In community-dwelling elderly individuals following physical capacity evaluations, anthropometric measurements, HGS, bioimpedance analysis, and muscle ultrasound for the measurement of biceps brachii muscle thickness were performed. The study population consisted of 156 participants; ICC for ultrasound measurements resulted in 0.96 and 95% CI 0.95-0.98, indicating excellent reliability. The Kruskal-Wallis analysis revealed that muscle thickness differed between age tertiles in both male (p = 0.0005) and female populations (p = 0.001). Regression analysis adjusted for age, sex, BMI, muscle mass in percentage, and comorbidities revealed a significant and independent positive correlation between muscle strength and muscle thickness: R² = 0.70, β = 0.9, 95% CI: 0.7-1.2, and p < 0.001 in male population and R² = 0.17, β = 0.2, 95% CI: 0.1-0.4, and p = 0.005 in female population. Muscle thickness of biceps brachii measured by ultrasound and handgrip strength is characterized by a significant and positive relationship in older adults. In both female and male populations, the reduction of muscle thickness is parallel to increased age. Implementation of noninvasive ultrasound evaluation of muscle thickness could be helpful in the early detection of physical decline associated with the aging process.

Keywords: Elderly; Handgrip strength; Muscle strength; Muscle thickness; Muscle ultrasound.