Abstract
Postexercise hypotension results from a persistent drop in peripheral vascular resistance. We tested the hypothesis that during postexercise hypotension, α-adrenergic responsiveness in leg skeletal muscle vascular beds is blunted. We studied 8 men and 1 woman before and 30-min after a 60-min bout of cycling at 60% VO2peak. Arterial pressure (femoral artery catheter) and femoral blood flow (Doppler ultrasound) were measured and vascular resistance was calculated during intraarterial infusions of the α1-agonist phenylephrine and the α2-agonist clonidine. Exercise reduced mean arterial pressure (80±2 vs 89±2 mmHg, P< 0.05) and femoral vascular resistance (0.15±0.03 vs 0.26±0.03 units, P< 0.05). Vasoconstriction to phenylephrine was similar post-exercise (215±54%) vs pre-exercise (172±47%, P= 0.49). Likewise, vasoconstriction to clonidine was similar post-exercise (156±34%) vs pre-exercise (114±31%, P= 0.41). Thus, while postexercise hypotension is associated with long-lasting reductions in vascular resistance in the leg, it does not appear that blunting of α-adrenergic responsiveness is the cause. Supported by AHA grant 30403Z.
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