Seven intermittent exposures to altitude improves exercise performance at 4300 m.
OBJECTIVE
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 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.


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.
Beidleman
Beth A
BA
Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. beth.beidleman@na.amedd.army.mil
Muza
Stephen R
SR
Fulco
Charles S
CS
Cymerman
Allen
A
Sawka
Michael N
MN
Lewis
Steven F
SF
Skrinar
Gary S
GS
D000222:Adaptation, Physiological; D000328:Adult; D000531:Altitude; D001642:Bicycling / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D011446:Prospective Studies; D012146:Rest / Q000502:physiology*; D013997:Time Factors