Limb-specific training affects exercise hyperemia but not sympathetic vasoconstriction

Abstract

This study used cross-sectional and longitudinal training research designs to determine if (a) exercise hyperemia is enhanced in exercise-trained forearms and (b) sympathetic vasoconstriction of the trained forearm is attenuated (sympatholysis) during handgrip exercise. In the cross-sectional comparison, 10 rock climbers, 10 runners, 10 controls participated while the longitudinal training study examined vascular responsiveness in six untrained men before and after 6weeks of handgrip training. Mean blood velocity, brachial artery diameter, heart rate, and systemic blood pressure were measured at rest, during a cold pressor test (CPT), dynamic handgrip exercise at 30% MVC with and without CPT, and during reactive hyperemia. During the resting CPT, forearm blood flow (FBF) decreased less (P<0.05) in runners than in climbers, the decline being -6.30+30.05 and -34.3+20.54 during the last minute, respectively. During handgrip exercise, FBF and vascular conductance (VC) increased more (P<0.05) in climbers than in runners and controls, the latter reaching 3.98+1.11, 2.22+0.88, and 2.75+1.06 mlmin(-1)mmHg(-1), respectively. When a CPT was added during handgrip exercise, the reduction in FBF and VC was not different between the groups. Handgrip training increased (P < 0.05) forearm volume (5 + 3%) and MVC (25 + 29%), but did not affect FBF or VC during a CPT, with or without exercise. These data suggest that arm-trained athletes have greater exercise hyperemia. However, this training effect is not explained by sympatholysis and is not evident after 6weeks of handgrip training in previously untrained subjects.