Comparison of an Intermittent Hypoxic Exposure Acclimatization Program to Staging at Moderate Altitude on Endurance Performance at 4300 m
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA THERMAL AND MOUNTAIN MEDICINE DIVISION
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Endurance performance decreases upon initial exposure to altitude but improves following acclimatization induced by continuous altitude residence. For low-altitude residents, acclimatization to a target altitude can be induced by temporarily residing staging at moderate altitudes. However, staging may not be available or logistically practical for low altitude-based Warfighters needing to rapidly ascend to high altitude. An alternative method for inducing altitude acclimatization, termed intermittent hypoxic exposure IHE, may provide an acceptable alternative for minimizing endurance performance decrements at altitude following rapid ascent. PURPOSE The purpose of this study was to compare the effects of one week of normobaric IHE to one week of staging STG at 2,200 m on endurance performance at 4,300 m altitude in healthy male lowlanders. METHODS Two studies were conducted using the same facilities, test equipment and investigators. IHE study 11 male lowlanders Mean or - S.E., age 22 or - 1 yr, VO2peak 47 or - 5 mlkgmin were initially Pre-T exposed to 4,300 m, followed by 12 days of sea level residence to deacclimatize, then 6-7 days of normobaric IHE hypoxia room 2 h PIO290 mmHg sedentary 1 h PIO2 110 mmHg exercising at 80 peak heart rate followed by a 60 hour delay at sea level and a second exposure Post-T to 4,300 m. STG study 10 male lowlanders age 21 or - 1 yrs, VO2peak 51 or - 7 mlkgmin were initially exposed to 4300 m before Pre-T and after Post-T staging for 6 d at 2,200 m. In both studies, subjects were tested on a cycle ergometer during 40 min steady-state exercise followed immediately by a 360 kJ maximum effort Time-Trial TT at sea level, and again beginning within 3 hrs of high altitude HA exposure to 4,300 m. During the TT, the men freely adjusted power output. Arterial oxygen saturation SaO2, heart rate HR, and ratings of perceived exertion RPE were measured every 5 min during exercise.
- Stress Physiology