Beidleman, B. A., Muza, S. R., Rock, P. B., Fulco, C. S., Lyons, T. P., Hoyt, R. W., & Cymerman, A. (1997). Exercise responses after altitude acclimatization are retained during introduction to altitude. Medicine and Science in Sports and Exercise, 29, 1588-1595.

"Following 2 to 3 wk of altitude acclimatization, ventilation is increased and heart rate, plasma volume, and lactate accumulation are decreased during submaximal exercise" (p. 1588). This investigation evaluated if any acclimatization responses would be retained upon reintroduction to altitude after eight days at sea level. Sea level males (N = 6) adapted for 16 days on Pike's Peak (4,300 m) and then returned to sea level. After eight days, Ss were reintroduced to simulated altitude in a hypobaric chamber (4,300 m) to assess adaptation retention.

Small subject numbers did not provide much statistical power for comparisons. The best submaximal performances to exhaustion occurred at sea level after altitude adaptation. During exercise (75% VO2peak), arterial oxygen saturation increased at the first altitude exposure and remained elevated at reintroduction to sea level and altitude. Heart rate decreased upon the first exposure to altitude and remained decreased upon the second exposure. Plasma volume decreased at altitude, sea level reintroduction, and altitude reintroduction. Lactate values decreased upon returning to sea level after altitude adaptation and increased again upon reintroduction to simulated altitude.

Implication. High altitude exercise adaptations are likely to be retained for more than eight days after reintroduction to sea level.

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