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1School of Kinesiology and Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario; 2School of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada; and 3Unite de Médecine et Physiologie Spatiale, Département de Médecine Nucléaire and Ultrasons, Centres Hospitaliers Universitaires Trousseau, Université de Tours, Trousseau, France
Submitted 23 November 2006 ; accepted in final form 28 March 2007
The mechanism of the pressor response to small muscle mass (e.g., forearm) exercise and during metaboreflex activation may include elevations in cardiac output (
) or total peripheral resistance (TPR). Increases in
must be supported by reductions in visceral venous volume to sustain venous return as heart rate (HR) increases. Therefore, this study tested the hypothesis that increases in
, supported by reductions in splanchnic volume (portal vein constriction), explain the pressor response during handgrip exercise and metaboreflex activation. Seventeen healthy women performed 2 min of static ischemic handgrip exercise and 2 min of postexercise circulatory occlusion (PECO) while HR, stroke volume and superficial femoral artery flow (Doppler), blood pressure (Finometer), portal vein diameter (ultrasound imaging), and muscle sympathetic nerve activity (MSNA; microneurography) were measured followed by the calculation of
, TPR, and leg vascular resistance (LVR). Compared with baseline, mean arterial blood pressure (MAP) (P < 0.001) and
(P < 0.001) both increased in each minute of exercise accompanied by a
5% reduction in portal vein diameter (P < 0.05). MAP remained elevated during PECO, whereas
decreased below exercise levels. MSNA was elevated above baseline during the second minute of exercise and through the PECO period (P < 0.05). Neither TPR nor LVR was changed from baseline during exercise and PECO. The data indicate that the majority of the blood pressure response to isometric handgrip exercise in women was due to mobilization of central blood volume and elevated stroke volume and
rather than elevations in TVR or LVR resistance.
cardiac output; microneurography; muscle sympathetic nerve activity; metaboreflex
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