Exercise responses after altitude acclimatization are retained during reintroduction to altitude

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Abstract
Exercise responses after altitude acclimatization are retained during reintroduction to altitude. Med. Sci. Sports Exerc., Vol. 29, No. 12, pp. 1588-1595, 1997. Following 2 to 3 wk of altitude acclimatization, ventilation is increased and heart rate (HR), plasma volume (PV), and lactate accumulation ([La]) are decreased during submaximal exercise. The objective of this study was to determine whether some degree of these exercise responses associated with acclimatization would be retained upon reintroduction to altitude (RA) after 8 d at sea level (SL). Six male lowlanders ([horizontal bar over]X ± SE; 31 ± 2 yr, 82.4 ± 4.6 kg) exercised to exhaustion at the same relative percentages of peak oxygen uptake(˙VO2peak) at SL, on acute altitude (AA) exposure, after a 16-d chronic altitude (CA) exposure on Pikes Peak (4,300 m), and during a 3- to 4-h RA in a hypobaric chamber (4,300 m; 446 mm Hg) after 8 d at SL. The submaximal exercise to exhaustion time (min) was the same at SL (66.0 ± 1.6), AA(67.7 ± 7.3), CA (79.9 ± 6.2), and RA (67.9 ± 1.9). At 75% ˙VO2peak: (1) arterial oxygen saturation (SaO2) increased from AA to CA (67.0 ± 1.5 vs 78.5 ± 1.8%; P-1