Local ischemic preconditioning improves skeletal muscle blood flow and vasodilation during exercise in older adults

Aging is associated with reduced blood flow responses in contracting skeletal muscle partially attributed to an impaired ability to offset sympathetic-mediated vasoconstriction. Ischemic preconditioning (IPC) attenuates sympathetic vasoconstrictor responsiveness in the forearm of young males. Therefore, we tested the hypothesis that IPC would improve vasoconstrictor responsiveness and exercise hyperemia in older adults. Eleven subjects (64±7 years) completed rhythmic handgrip exercise trials before and after one of three intervention periods: remote IPC (non-exercising arm), local IPC (exercising arm), or time control (TC). IPC interventions involved four cycles of 5 minutes upper arm occlusion followed by 5 minutes reperfusion, whereas TC involved no cuff occlusion. Lower body negative pressure (LBNP) was used to elicit sympathetic-mediated vasoconstriction during the handgrip trials. Forearm blood flow (FBF; ml/min) was measured via Doppler ultrasound, with forearm vascular conductance (FVC; ml·min ^-1 ·100 mmHg ^-1 ) calculated as the quotient of FBF and mean arterial pressure. % change in FVC in response to LBNP during handgrip exercise was used to assess vasoconstrictor responsiveness. Local IPC attenuated the reduction in FVC from pre to post (-15.4±4.1 to -9.3±5.4%, P<0.001), whereas no change was observed with remote IPC (-13.4±3.4 to -11.9±2.5%, P=0.11) and TC (-14.4±3.5 to -13.8±4.1%, P=0.52). Additionally, the changes (Δ) in FBF (154±61 to 182±59 ml/min, P<0.001) and FVC (151±59 to 174±60 ml·min ^-1 ·100 mmHg ^-1 , P=0.002) from baseline to steady state exercise were increased following local IPC, but not remote IPC. Our data demonstrate that application of local IPC acutely improves exercise hyperemia and reduces sympathetic-mediated-vasoconstriction in skeletal muscle of older adults.