Exercise responses after altitude acclimatization are retained during reintroduction to altitude

BEIDLEMAN, BETH A.; MUZA, STEPHEN R.; ROCK, PAUL B.; FULCO, CHARLES S.; LYONS, TIMOTHY P.; HOYT, REED W.; CYMERMAN, ALLEN

Medicine & Science in Sports & Exercise:
Basic Sciences: Original Investigations
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< 0.05) and remained increased at RA (77.0 ± 2.0%); (2) HR decreased from SL to CA (171 ± 6 vs 152 ± 9 beats·min-1;P < 0.05) and remained decreased at RA (157 ± 5 beats·min-1); (3) calculated PV decreased 6.9 ± 10.0% at AA, 21.3 ± 11.1% at CA, and 16.7 ± 5.4% at RA from SL baseline values, and (4) [La] decreased from AA to CA (5.1 ± 0.9 vs 1.9 ± 0.4 mmol·L-1; P < 0.05) and remained decreased at RA (2.6 ± 0.6 mmol·L-1). Upon RA after 8 d at SL, the acclimatization responses were retained 92 ± 9% for SaO2, 74± 8% for PV, and 58 ± 3% for [La] at 75% ˙VO2peak. In conclusion, although submaximal exercise to exhaustion time is not improved upon reintroduction to altitude after 8 d at sea level, retention of beneficial exercise responses associated with altitude acclimatization is likely in individuals whose work, athletic competition, or recreation schedules involve intermittent sojourns to high elevations.

Author Information

Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760

Submitted for publication January 1997.

Accepted for publication August 1997.

©1997The American College of Sports Medicine