Hypovolemia during exercise in the heat significantly increased forearm vascular resistance at the onset of exercise compared to normovolemia (27.1 vs 13.2 units) to preserve blood pressure.
Does hypovolemia affect forearm vascular resistance control during dynamic exercise in the heat in physically active men?
Hypovolemia during exercise in the heat causes an increase in forearm vascular resistance, thereby preserving arterial blood pressure and adequate perfusion to essential organs.
Absolute Event Rate: 27.1% vs 13.2%
To determine the influence of hypovolemia on the control of forearm vascular resistance (FVR) during dynamic exercise, we studied five physically active men during 60 min of supine cycle ergometer exercise bouts at 35 degrees C in control (normovolemic) and hypovolemic conditions. Hypovolemia was achieved by 3 days of diuretic administration and resulted in an average decrease in plasma volume of 15.9%. Relative to normovolemia, hypovolemia caused an attenuation of the progressive rise in forearm blood flow (P less than 0.05) and an increase in heart rate (P less than 0.05) during exercise. Because mean arterial blood pressure during hypovolemic exercise was well maintained, the attenuation of forearm blood flow was due entirely to a relative increase in FVR. At the onset of dynamic exercise, FVR was increased significantly in control and hypovolemic conditions by 13.2 and 27.1 units, respectively. The increase in FVR was significantly different between control and hypovolemic conditions as well. We attributed the increased vasoconstrictor bias during hypovolemia to cardiopulmonary baroreceptor unloading and/or an increased sensitivity to cardiopulmonary baroreceptor unloading. We concluded that reduced blood flow to the periphery during exercise in the hypovolemic condition was caused entirely by an increase in vascular resistance, thereby preserving arterial blood pressure and adequate perfusion to the organs requiring increased flow.
Nishiyasu et al. (Tue,) conducted a other in Exercise in the heat (n=5). Hypovolemia (diuretic administration) vs. Normovolemia (control) was evaluated on Increase in forearm vascular resistance (FVR) at the onset of dynamic exercise. Hypovolemia during exercise in the heat significantly increased forearm vascular resistance at the onset of exercise compared to normovolemia (27.1 vs 13.2 units) to preserve blood pressure.
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