title: The influence of acute and 23 days of intermittent hypoxic exposures on the exercise-induced forehead sweating response.
abstract: The effect of acute and 23 days of intermittent exposures to normobaric hypoxia on the forehead sweating response during steady-state exercise was investigated. Eight endurance athletes slept in a normobaric hypoxic room for a minimum of 8 h per day at a simulated altitude equivalent to 2,700 m for 23 days (sleep high-train low regimen). Peak oxygen uptake (VO2(peak)) and peak work rate (WR(peak)) were determined under normoxic (20.9%O(2)) and hypoxic (13.5%O(2)) conditions prior to (pre-IHE), and immediately after (post-IHE) the intermittent hypoxic exposures (IHE). Also, each subject performed three 30-min cycle-ergometry bouts: (1) normoxic exercise at 50% WR(peak) attained in normoxia (control trial; CT); (2) hypoxic exercise at 50% WR(peak) attained in hypoxia (hypoxic relative trial; HRT) and (3) hypoxic exercise at the same absolute work rate as in CT (hypoxic absolute trial; HAT). Exposure to hypoxia induced a 33 and 37% decrease (P < 0.001) in (VO2(peak)) pre-IHE and post-IHE, respectively. Despite similar relative oxygen uptake during HAT pre-IHE and post-IHE, the ratings of perceived whole-body exertion decreased substantially (P < 0.05) post-IHE. Pre-IHE the sweat secretion on the forehead (m(sw)f) was greater (P < 0.01) in the HAT (2.60 (0.80) mg cm(-2) min(-1)) compared to the other two trials (CT = 1.87 (1.09) mg cm(-2) min(-1); HRT = 1.57 (0.82) mg cm(-2) min(-1)) despite a similar exercise-induced elevation in body temperatures, resulting in an augmented (P < 0.01) gain of the sweating response (m(sw)f/Delta T(re)). The augmented (m(sw)f) and m(sw)f/Delta T(re) during the HAT were no longer evident post-IHE. Thus, it appears that exercise sweating on the forehead is potentiated by acute exposure to hypoxia, an effect which can be abolished by 23 days of intermittent hypoxic exposures.
authors.affiliation: Department of Automation, Biocybernetics and Robotics, Institute Jozef Stefan, Jamova 39, Ljubljana, 1000, Slovenia. alan.kacin@vsz.uni-lj.si
authors.forename: Alan
authors.initials: A
authors.lastname: Kacin
authors.forename: Petra
authors.initials: P
authors.lastname: Golja
authors.forename: Ola
authors.initials: O
authors.lastname: Eiken
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Tipton
authors.forename: Igor B
authors.initials: IB
authors.lastname: Mekjavic
mesh_terms: D000064:Acclimatization; D000208:Acute Disease; D000328:Adult; D000531:Altitude; D001794:Blood Pressure; D001833:Body Temperature Regulation; D002908:Chronic Disease; D004906:Erythrocyte Count; D015444:Exercise; D005260:Female; D005546:Forehead; D006339:Heart Rate; D006400:Hematocrit; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption; D005082:Physical Exertion; D015656:Respiratory Mechanics; D012881:Skin Temperature; D013546:Sweating; D013997:Time Factors
chemical_list: D019344:Lactic Acid