Submitted on December 18, 2002
Accepted on June 17, 2003
Intermittent Altitude Exposures Improve Muscular Performance at 4300 M
Beth A Beidleman1*, Stephen R Muza1, Charles S Fulco1, Allen Cymerman1, Dan T Ditzler1, Dean Stulz1, Janet E Staab1, Scott R Robinson1, Gary S Skrinar2, Steven F Lewis2, and Michael N Sawka1
1 Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, MA, USA
2 Department of Health Sciences, Boston University, Sargent College of Health and Rehabilitation Sciences, Boston, MA, USA
* To whom correspondence should be addressed. E-mail: beth.beidleman{at}na.amedd.army.mil.
Chronic altitude residence improves muscular performance at altitude but the effect of intermittent altitude exposures (IAE) on muscular performance at altitude has not been defined. The purpose of this study was to determine the effects of 3 wk of IAE, in combination with rest and cycle training, on muscular performance at altitude. Six lowlanders (Mean±SE; 23±2 yr, 77±6 kg) completed a cycle time trial and adductor pollicis endurance test at sea level and during a 30 h acute exposure to 4300 m altitude equivalent (PB=446 mmHg) once before (PreIAE) and once after (PostIAE) a 3-wk period of IAE (4h.d-1, 5 d.wk-1, 4300 m). During each IAE, three subjects cycled for 45-60 min.d-1 at 60%-70% of VO2max and three subjects rested. Cycle training during each IAE did not affect muscular performance at altitude. Thus, data from all six subjects were combined. Three wk of IAE resulted in: (1) a 21±6% improvement (P<0.05) in cycle time-trial performance (min) from PreIAE (32.8±3.7) to PostIAE (24.8±1.2) (2) a 63±26% improvement (P<0.05) in adductor pollicis endurance (min) from PreIAE (9.2±2.8) to PostIAE (14.8±4.2), and (3) a 10±4% increase (P<0.05) in resting arterial O2 saturation (SaO2;%) from PreIAE (82±2) to PostIAE (90±1). These improvements in muscular performance following IAE correlated strongly with increases in resting SaO2 and were comparable to those reported previously following chronic altitude residence. IAE may therefore be used as an alternative to chronic altitude residence to facilitate improvements in muscular performance in athletes, soldiers, mountaineers, shift workers, and others that are deployed to altitude.
