This study investigated the physiological and gender determinants of the age-related loss of muscle power in 31 healthy middle-aged adults (aged 40-55 years), 28 healthy older adults (70-85 years) and 34 mobility-limited older adults (70-85 years). We hypothesized that leg extensor muscle power would be signiWcantly lower in mobilitylimited elders relative to both healthy groups and sought to characterize the physiological mechanisms associated with the reduction of muscle power with aging. Computed tomography was utilized to assess mid-thigh body composition and calculate speciWc muscle power and strength. Surface electromyography was used to assess rate of neuromuscular activation and muscle biopsies were taken to evaluate single muscle Wber contractile properties. Peak muscle power, strength, muscle cross-sectional area, speciWc muscle power and rate of neuromuscular activation were signiWcantly lower among mobility-limited elders compared to both healthy groups (P≤ 0.05). Mobility-limited older participants had greater deposits of intermuscular adipose tissue (P < 0.001). Single Wber contractile properties of type I and type IIA muscle Wbers were preserved in mobility-limited elders relative to both healthy groups. Male gender was associated with greater decrements in peak and speciWc muscle power among mobility-limited participants. Impairments in the rate of neuromuscular activation and concomitant reductions in muscle quality are important physiological mechanisms contributing to muscle power deWcits and mobility limitations. The dissociation between age-related changes at the whole muscle and single Wber level suggest that, even among older adults with overt mobility problems, contractile properties of surviving muscle Wbers are preserved in an attempt to maintain overall muscle function.
- Muscle power
- Single muscle Wber properties
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Public Health, Environmental and Occupational Health
- Physiology (medical)