Exercise Overcomes Aging Associated Inhibition in Sympatholysis

Contracting skeletal muscle can overcome sympathetic vasoconstriction during sub‐maximal exercise. In contrast, maximal whole‐body exercise appears to cause selective sympathetic vasoconstriction as muscle blood flow is restricted despite an increase in blood pressure. Previous work has suggested that aging results in an inhibition of sympatholysis in response to pharmacologic agents, but it remains unknown if exercise can overcome this reported inhibition of sympatholysis and if physical activity can offset the reported age related loss in sympatholysis. Methods On two separate experimental days, we measured: 1) Leg hemodynamics during knee‐extensor exercise and arterial infusion of ATP and ACH with and without co‐infusion of Tyramine, and 2) leg and systemic hemodynamics during incremental one‐legged cycling, two‐legged cycling and combined arm and two‐legged cycling in seven older trained (62±2 years, 73±3 kg, 42±3 ml/min/kg) and 8 older untrained (65±3 years, 80±4 kg, 24±1 ml/min/kg) subjects. Tyramine blunted the vasodilatory response to exercise and ATP in the untrained subjects, whereas it was maintained in the trained subjects. During exercise, leg blood flow was lower during two‐legged cycling compared to one‐legged cycling in both groups and the addition of arm‐exercise inhibited the leg blood flow response further. However, the rate of rise in leg blood flow pr watt was lower in the untrained subjects in all trials. These studies demonstrate that exercise training overcomes the reported age‐related attenuation in sympatholysis in response to both acute exercise and pharmacologic agents. They also demonstrate the impact of exercise training on the aging phenotype. Supported by the Augustinus foundation and by NIH RM‐07‐007