title: Reduction in Cerebral Oxygenation After Prolonged Exercise in Hypoxia is Related to Changes in Blood Pressure.
abstract: We investigated the relation between blood pressure and cerebral oxygenation (COX) immediately after exercise in ten healthy males. Subjects completed an exercise and recovery protocol while breathing either 21% (normoxia) or 14.1% (hypoxia) O2 in a randomized order. Each exercise session included four sets of cycling (30 min/set, 15 min rest) at 50% of altitude-adjusted peak oxygen uptake, followed by 60 min of recovery. After exercise, mean arterial pressure (MAP; 87±1 vs. 84±1 mmHg, average values across the recovery period) and COX (68±1% vs. 58±1%) were lower in hypoxia compared to normoxia (P<0.001). Changes in MAP and COX were correlated during the recovery period in hypoxia (r=0.568, P<0.001) but not during normoxia (r=0.028, not significant). These results demonstrate that reductions in blood pressure following exercise in hypoxia are (1) more pronounced than in normoxia, and (2) associated with reductions in COX. Together, these results suggest an impairment in cerebral autoregulation as COX followed changes in MAP more passively in hypoxia than in normoxia. These findings could help explain the increased risk for postexercise syncope at high altitude.
authors.affiliation: Division of Human Environmental Science, Mt. Fuji Research Institute, Fujiyoshida, Japan. mhoriuchi@mfri.pref.yamanashi.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Horiuchi
authors.affiliation: Division of Human Environmental Science, Mt. Fuji Research Institute, Fujiyoshida, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Dobashi
authors.affiliation: Division of Human Environmental Science, Mt. Fuji Research Institute, Fujiyoshida, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Kiuchi
authors.affiliation: Division of Human Environmental Science, Mt. Fuji Research Institute, Fujiyoshida, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Endo
authors.affiliation: Division of Human Environmental Science, Mt. Fuji Research Institute, Fujiyoshida, Japan.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Koyama
authors.affiliation: Department of Biology, University of Colorado Colorado Springs, Colorado Springs, CO, USA.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Subudhi
mesh_terms: D000328:Adult; D000531:Altitude; D062186:Arterial Pressure / Q000502:physiology*; D001921:Brain / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D013575:Syncope / Q000209:etiology
chemical_list: D010100:Oxygen
keywords: Cerebral autoregulation; High altitude; Near infrared spectroscopy; Postexercise syncope; Vasodilation