Comparison of an Intermittent Hypoxic Exposure Acclimatization Program to Staging at Moderate Altitude on Endurance Performance at 4300 m.

摘要

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 ml/kg/min) were initially (Pre-T) exposed to 4,300 m, followed by approximately 12 days of sea level residence to deacclimatize, then 6-7 days of normobaric IHE (hypoxia room: 2 h PIO2=90 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 ml/kg/min) 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.