Exercise Performance of Sea-Level Residents at 4300 m After 6 Days at 2200 m
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA THERMAL AND MOUNTAIN MEDICINE DIVISION
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Partial acclimatization resulting from staging at moderate altitude reduces acute mountain sickness during rapid exposure to higher altitudes e.g., 4300 m. Whether staging also benefits endurance performance has not yet been scientifically evaluated. Purpose Determine the effectiveness of staging at 2200 m on time trial TT performance of unacclimatized sea-level residents SLR during rapid exposure to 4300 m. There were 10 healthy men mean - SE 21 - 1 yrs who performed 720 kJ cycle TT at SL and following 2 h of exposure to 4300 m 459 Torr before ALT-1 and after ALT-2 living for 6 d at 2200 m 601 Torr. Methods Hemoglobin concentration Hb, hematocrit Hct, arterial oxygen saturation SaO2, ratings of perceived exertion RPE, and heart rate HR were measured before and during exercise. Results Compared to SL 73 - 6 min, TT performance was impaired P 0.01 by 38.1 - 6 min at ALT-1, but only by 18.7 - 3 min at ALT-2. The 44 - 8 TT improvement at 4300 m was directly correlated with increases in exercise SaO2 R 0.88, P 0.03, but not to changes in Hb or Hct. In addition, RPE was lower 13 - 1 vs. 16 - 1, P 0.01 and HR remained at 148 - 5 bpm despite performing the TT at a higher power output during ALT-2 than ALT-1 120 - 7 vs. 100 - 10 W, P 0.01. Conclusion Partial acclimatization resulting from staging attenuated the impairment in TT performance of SLR rapidly exposed to 4300 m. The close association between improved TT performance and changes in exercise SaO2, compared to a lack of association with changes in Hb or Hct, suggest ventilatory acclimatization may have been the major factor contributing to the performance improvement.
- Stress Physiology