[Physical exercise impairs the acute stage of adaptation to moderate altitude]

A recent study has reported the impairment of high altitude adaptation capacity by physical exercise in a decompression chamber. The aim of our protocol was to evaluate if physical exercise at moderate altitude in the Alps would show a similar effect. 8 alpinists were examined in a randomised cross-over trial at 171 m and at 3000 m altitude under sedentary and under exercise condition (50% maximal workload on the bicycle ergometer four times 30 minutes during the first 6 hours of an 8 hour observation period at each altitude). At the beginning and at the end of each observation period AMS scores and arterial oxygen saturation SaO2 were measured. The differences of the AMS scores and the differences of SaO2 at both test conditions were compared at both altitudes.

In comparison to sedentary condition, the differences between initial and final AMS scores at 3000 m altitude were significantly higher (-0.38 +/- 0.52 vs. -1.25 +/- 0.46, diff 0.88, 95% CI 0.58 to 1.17, p < 0.01), as well as the difference between initial and final SaO2 (-0.25 +/- 0.71% vs. 2.25 +/- 1.04%, diff. -2.5%, 95% CI for the diff. -3.59 to -1.41, p < 0.01). AMS score and SaO2 did not change after exercise at 171 m altitude.

Physical exercise impairs the acute stage of adaptation to moderate altitude. This is mainly due to the exercise-induced exaggeration of arterial hypoxaemia.