We examined the interactive influence of hypoxia and exercise, and hypercapnia and exercise, on regional cerebral perfusion and sympathetic activation. Twenty healthy young adults (seven women) completed study trials including (1) rest in normoxia ( : ∼96%, : ∼36 mmHg), normocapnic hypoxia ( : ∼84%, : ∼36 mmHg), and normoxic hypercapnia ( : ∼98%, : ∼46 mmHg) and (2) unilateral rhythmic handgrip exercise (45% of maximal voluntary contraction at 1 Hz for 3 min) under the same gas conditions. Based on the exercising arm, blood flow in the contralateral internal carotid (ICA) and ipsilateral vertebral (VA) arteries, anterior and posterior cerebral O delivery ( ), and muscle sympathetic nerve activity (MSNA) were measured in each trial.
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