A-15R Free Communication/Poster Peripheral Circulation
We sought to determine whether α-adrenergic control of skeletal muscle blood flow is altered in trained athletes at rest and during exercise. Furthermore, the blood flow responses to selective α-adrenergic agonist administration were assessed to delineate α-1 vs. α-2 receptor mediated vasoconstriction.
Mean arterial pressure (MAP), femoral blood flow (FBF, Doppler), and muscle tissue oxygenation (TOm, near-infrared) were measured in 5 average fit (AF) and 5 high fit (HF) men during randomized arterial infusion of phenylephrine (PE, α-1 agonist) or BHT-933 (BH, α-2 agonist) at rest and during dynamic knee extension exercise at 27W.
At rest and during exercise, MAP, FBF, and femoral vascular conductance were not different between AF and HF subjects. Following PE (0.8μg/kg/min), FBF decreased more in HF (−193 ± 67ml/min) than AF (−97 ± 24ml/min) subjects (P < 0.05), while the change in TOm was similar between groups. BH (20μg/kg/min) produced comparable changes in resting FBF, whereas changes in TOm were significantly greater in HF (38 ± 5%) than AF (20 ± 3%) subjects (P < 0.05). During exercise, percent changes in FBF following flow-adjusted PE and BH infusion were reduced compared to rest. Furthermore, the PE-induced flow response (rest vs. exercise) was attenuated more in HF (−53 ± 14% vs. −10 ± 5%) than in AF (−20 ± 11% vs. −12 ± 8%).
These data suggest that aerobic fitness may improve the fine control of active skeletal muscle blood flow and optimize regional distribution of blood flow at rest and during exercise. Supported in part by NIH5547, NASA (NAG9-1262), Danish Research Council, The Danish Basic Research, Kaj Hansens and Danish Heart Foundations.