• Beth A Beidleman, Stephen R Muza, Charles S Fulco, Allen Cymerman, Michael N Sawka, Steven F Lewis, and Gary S Skrinar.
• Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. beth.beidleman@na.amedd.army.mil
• Med Sci Sports Exerc. 2008 Jan 1; 40 (1): 141-8.

PurposeThe purpose of this study was to determine whether seven intermittent altitude exposures (IAE), in combination with either rest or exercise training, improves time-trial exercise performance and induces physiologic adaptations consistent with chronic altitude adaptation at 4300 m.MethodsTen adult lowlanders (26 +/- 2 yr; 78 +/- 4 kg; means +/- SE) completed cycle endurance testing during an acute exposure to a 4300-m-altitude equivalent (446 mm Hg) once before (pre-IAE) and once after (post-IAE) 7 d of IAE (4h x d(-1), 5 d x wk(-1), 4300 m). Cycle endurance testing consisted of two consecutive 15-min constant-work rate exercise bouts followed immediately by a time-trial exercise performance test. During each IAE, five subjects performed exercise training, and the other group of five subjects rested.ResultsBoth groups demonstrated similar improvements in time-trial cycle exercise performance and physiologic adaptations during constant-work rate exercise from pre-IAE to post-IAE. Thus, data from all subjects were combined. Seven days of IAE resulted in a 16% improvement (P < 0.05) in time-trial cycle exercise performance (min) from pre-IAE (35 +/- 3) to post-IAE (29 +/- 2). During the two constant-work rate exercise bouts, there was an increase (P < 0.05) in exercise arterial O2 saturation (%) from pre-IAE (77 +/- 2; 75 +/- 1) to post-IAE (80 +/- 2; 79 +/- 1), a decrease (P < 0.05) in exercise heart rate (bpm) from pre-IAE (136 +/- 6; 162 +/- 5) to post-IAE (116 +/- 6; 153 +/- 5), and a decrease (P < 0.05) in exercise ratings of perceived exertion from pre-IAE (10 +/- 1; 14+/- 1) to post-IAE (8 +/- 1; 11 +/- 1).ConclusionsOur findings indicate that 7 d of IAE, in combination with either rest or exercise training, improves time-trial cycle exercise performance and induces physiologic adaptations during constant-work rate exercise consistent with chronic altitude adaptation at 4300 m.

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