Effect of continuous negative-pressure breathing on skin blood flow during exercise in a hot environment |
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Authors: | Nagashima, Kei Nose, Hiroshi Takamata, Akira Morimoto, Taketoshi |
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Abstract: | To assessthe impact of continuous negative-pressure breathing (CNPB) on theregulation of skin blood flow, we measured forearm blood flow (FBF) byvenous-occlusion plethysmography and laser-Doppler flow (LDF) at theanterior chest during exercise in a hot environment (ambienttemperature = 30°C, relative humidity = ~30%). Seven malesubjects exercised in the upright position at an intensity of 60% peakoxygen consumption rate for 40 min with and without CNPB after 20 minof exercise. The esophageal temperature(Tes) in both conditionsincreased to 38.1°C by the end of exercise, without any significantdifferences between the two trials. Mean arterial pressure (MAP)increased by ~15 mmHg by 8 min of exercise, without any significantdifference between the two trials before CNPB. However, CNPB reducedMAP by ~10 mmHg after 24 min of exercise (P < 0.05). The increasein FBF and LDF in the control condition leveled off after 18 min ofexercise above a Tes of37.7°C, whereas in the CNPB trial the increase continued, with arise in Tes despite the decreasein MAP. These results suggest that CNPB enhances vasodilation of skinabove a Tes of ~38°C bystretching intrathoracic baroreceptors such as cardiopulmonarybaroreceptors. |
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