Limb-specific training affects exercise hyperemia but not sympathetic vasoconstriction

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 6 weeks 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 ml min⁻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 6 weeks of handgrip training in previously untrained subjects.