Purpose: The 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.
Methods: Ten 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·d−1, 5 d·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.
Results: Both 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).
Conclusions: Our 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.
1Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, MA; and 2Department of Health Sciences, Sargent College of Health and Rehabilitation Sciences, Boston University, Boston, MA
Address for correspondence: Beth A. Beidleman, ScD, Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, MA 01760; E-mail: firstname.lastname@example.org.
Submitted for publication April 2007.
Accepted for publication August 2007.