Association of skeletal muscle microvascular function with physical fitness and body composition in older adults

Age-related declines in muscle function and mobility are often linked to vascular aging, including endothelial dysfunction and reduced capillary density. This cross-sectional study explored the relationship between skeletal muscle microvascular function and body composition as well as physical fitness in older adults. Sixty older adults ( n = 17 males; aged 60–75) were enrolled. Microvascular function of the medial gastrocnemius (MG) and tibialis anterior (TA) muscles was assessed using near-infrared spectroscopy. Key metrics included reoxygenation rate following occlusion (TSI10) and reoxygenation amplitude (TSI_recovery). Body composition was measured via DXA. Physical fitness assessments included grip strength, the timed up-and-go test, the 30-second sit-to-stand test, spatiotemporal gait performance measured using the GAITRite walkway, and the 6-minute walk test. VO 2 max was estimated from 6-minute walk performance. Relationships were examined using Pearson correlations and multiple regression models. TA TSI_recovery was positively correlated with estimated VO₂max and grip strength, and negatively correlated with fat mass index and body fat percentage (all p < 0.05). MG TSI_recovery and TSI10 showed stronger associations with adiposity and more limited associations with estimated VO₂max and gait swing time. MG TSI10 was negatively correlated with total fat mass, FMI, and BF% (all p < 0.001) and positively correlated with estimated VO₂max and 6-minute walk distance ( p < 0.05). In models adjusted for covariates, MG microvascular indices remained associated with lower adiposity and higher estimated VO 2 max (all p < 0.05). Skeletal muscle microvascular function is associated with adiposity and selected performance-related outcomes in older adults, with MG microvascular responsiveness being the most consistent. These findings suggest that microvascular measures may be potentially informative for age-related changes in body composition and physical fitness, but longitudinal studies are needed to determine their prognostic or mechanistic significance.