Effects of Healthy Aging and Cardiovascular Disease on Skin Blood Flow during Normothermic Exercise

Abstract

Purpose: Chronic adaptations in circulatory structure and function with healthy aging and ischaemic heart disease (IHD) may impair cutaneous (skin) blood flow (SkBF) and vascular conductance (CVC) during exercise, ultimately limiting exercise performance. It is unclear whether local cutaneous vasomotor control and responsiveness during exercise are altered with aging and IHD. Methods: Forearm SkBF (laser Doppler flowmetry) was assessed in 10 healthy young men (HY, 24±4 years), 10 healthy older men (HO, 58±6 years), and 9 older men with IHD (61±8 years) during seated upright rest (baseline) and exercise at 60±5% (moderate intensity) and 75±5% (vigorous intensity) of peak oxygen uptake (V̇ O2peak) in normothermic (thermal-neutral) conditions. CVC was calculated as perfusion units/mean arterial pressure. In a separate testing session, resting and exercise conditions were repeated while local skin temperature was clamped at 37°C to examine cutaneous vasomotor responsiveness to an additional vasodilatory stimulus. A secondary forearm site was used to investigate cutaneous vasomotor control via withdrawal of local sensory input with a topical anaesthetic treatment (EMLA cream). Repeated measures ANOVAs were performed to determine the effect of aging and IHD across experimental conditions in the unclamped/untreated skin (control), temperature-clamped skin, and EMLA-treated skin. Results: V̇ O2peak was not significantly different between HY and HO (mean±SD, 46±6 vs. 44±6 ml·kg-1·min-1, p=0.236) but was ~34% lower in IHD (29±6 ml·kg-1·min-1, p<0.001 vs. HO). Neither aging nor IHD had a significant effect on SkBF and CVC in the control skin site during exercise (all p≥0.153). SkBF and CVC were increased in temperature-clamped (p<0.001 for both SkBF and CVC) and EMLA-treated (p=0.003 for both SkBF and CVC) skin compared to control skin; however, there were no significant aging or IHD effects for SkBF and CVC in the temperature-clamped or EMLA-treated conditions (all p≥0.066). Conclusion: SkBF and CVC were not significantly impaired with aging or IHD during moderate and vigorous intensity, normothermic exercise. Likewise, exercise SkBF and CVC were not significantly different between groups with the addition of a powerful vasodilatory stimulus or withdrawal of sensory input, suggesting that cutaneous vasomotor control and responsiveness appear to be generally well-preserved in aging adults with and without IHD during normothermic exercise.