Cardiovascular responses to muscle ischemia in man--dependency on muscle mass

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Abstract
Whether the pressor response to exercise-induced muscle ischemia is related to the mass of tissue rendered ischemic was studied. Six men repeatedly exercised for 5 min at a fixed load between 75-150 W (bicycle ergometer). Thirty seconds before the end of exercise, circulation to 1 calf, 2 calves, 1 leg and 2 legs was arrested with pneumatic cuffs in successive tests with 15 min recovery periods interspersed. Each occlusion was maintained until the 3rd min of exercise recovery. During postexercise occlusion mean arterial pressure (MAP) was elevated in proportion to the mass of ischemic muscle, forearm blood flow (FBF) was elevated during the overlap of occlusion with exercise but did not show a uniform response during the following 3 min of occlusion, vasoconstriction or vasodilation occurred, heart rate (HR) was elevated only when 2 legs were occluded and occlusion did not affect ventilation or end-tidal CO2. The ischemic pressor response is muscle mass-dependent and the baroreflex alters peripheral vascular resistance to aid in elevated MAP maintenance.