Age-associated impairments in exercise tolerance and critical power are related to vascular endothelial dysfunction

Abstract

Background: Aging results in lower exercise tolerance, manifested as decreased Critical Power (CP). Aging is also associated with reduced physical activity, decreased muscle mass, and impaired vascular endothelial function, all of which may contribute to the age-related decrease in CP. Purpose: The purpose of this study was to determine if the age-related decrease in CP occurs independently of changes in physical activity and muscle mass and if it is related to impaired vascular endothelial function. Methods: 10 Old (63.1 ± 2.5 years, 5 female and 5 male) and 10 Young (24.4 ± 4.0 years, 5 female and 5 male) physically active volunteers enrolled in this study. Physical activity was measured with accelerometry. Leg muscle mass was quantified with dual x-ray absorptiometry (DEXA). CP during single leg knee extension exercise was determined over the course of 4 visits with 3-5 constant-power tests to task failure. On the fifth visit, vascular function of the leg was assessed with the passive leg movement (PLM) hyperemia. Results: Young and Old subjects did not differ in daily step count (Old = 13001.1 ± 2464.0 vs Young = 13527.0 ± 3213.8 steps, P = 0.735) or in leg lean mass (P = 0.901). The Old subjects had a lower mass-specific CP (Old = 3.20 ± 0.94 vs Young = 4.60 ± 0.87 W/kg, P = 0.004). The Old subjects also had significantly lower vascular function assessed by the peak hyperemic response to PLM, even after being normalized for leg-lean mass (Old = 79.4 ± 38.3 vs Young = 128.8 ± 34.9 ml/min/kg, P = 0.010). CP was related to PLM hyperemia (R= 0.63; P = 0.004). Importantly, simultaneously controlling for physical activity (steps per day) and for leg lean mass with partial correlation analysis, actually strengthened the relationship between CP and vascular function assessed by PLM (R = 0.69; P = 0.003). Conclusion: The age-related decline in CP is not merely the consequence of low physical activity or reduced muscle mass. Reductions in the vascular endothelial function within the exercising muscle are strongly related to the observed decline in CP. Future research should determine if interventions known to improve vascular function can ameliorate exercise tolerance in Old adults. BYU College Undergraduate Research Award This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.