J Physiol. 2021 May 25. doi: 10.1113/JP281691. Online ahead of print.
ABSTRACT
KEY POINTS: Healthy older adults exhibit lower cardiorespiratory fitness (VO2 peak) than young in the absence of any age-related difference in skeletal muscle mitochondrial capacity, suggesting central hemodynamics plays a larger role in age-related declines in VO2 peak. Total physical activity did not differ by age, but moderate-to-vigorous physical activity was lower in older compared to young adults. Moderate-to-vigorous physical activity is associated with VO2 peak and muscle oxidative capacity, but physical inactivity cannot entirely explain the age-related reduction in VO2 peak.
ABSTRACT: Declining fitness (VO2 peak) is a hallmark of aging and believed to arise from decreased oxygen delivery and reduced muscle oxidative capacity. Physical activity is a modifiable lifestyle factor that is critical when evaluating the effects of age on parameters of fitness and energy metabolism. The objective was to evaluate the effects of age and sex on VO2 peak, muscle mitochondrial physiology, and physical activity in young and older adults. An additional objective was to assess the contribution of skeletal muscle oxidative capacity to age-related reductions in VO2 peak and determine if age-related variation in VO2 peak and muscle oxidative capacity could be explained on the basis of physical activity levels. 23 young and 52 older men and women completed measurements of VO2 peak, mitochondrial physiology in permeabilized muscle fibers, and free-living physical activity by accelerometry. Regression analyses were used to evaluate associations between age and VO2 peak, mitochondrial function, and physical activity. Significant age-related reductions were observed for VO2 peak (P<0.001), but not muscle mitochondrial capacity. Total daily step counts did not decrease with age, but older adults showed lower moderate-to-vigorous physical activity, which was associated with VO2 peak (R2 = 0.323, P<0.001) and muscle oxidative capacity (R2 = 0.086, P = 0.011). After adjusting for sex and physical activity, age was negatively associated with VO2 peak but not muscle oxidative capacity. Healthy older adults exhibit lower VO2 peak but preserved mitochondrial capacity compared to young. Physical activity, particularly moderate-to-vigorous, is a key factor in observed age-related changes in fitness and muscle oxidative capacity, but cannot entirely explain the age-related reduction in VO2 peak. This article is protected by copyright. All rights reserved.
PMID:34032280 | DOI:10.1113/JP281691
