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Resumen:
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The objective of this study was to investigate if prolonged training at moderate altitude leads to complete acclimatization of maximal oxygen uptake (VO2max), and if physical activity at this altitude promotes additional skeletal muscle adaption. VO2max and biochemical analysis in biopsies of the vastus lateralis muscle were determined in nine moderately trained endurance athletes (A) and six inactive control subjects (C) during 6 weeks altitude training at 2800 m. VO2max was decreased after 1 day of altitude exposure compared with baseline values at 670 m in A (44.4 ± 4.2 ml·kg?1·min?1 vs. 50.1 ± 4.1, p ? 0.01) and C (38.7 ± 5.0 ml·kg?1·min?1 vs. 42.1 ± 4.6, p ? 0.05), and was completely restored after 44 days at altitude in both groups (A, 50.0 ± 5.7 ml·kg?1·min?1; C, 42.8 ± 5.1). Upon return from altitude, VO2max increased as compared to the baseline values in A (55.4 ± 6.3 ml·kg?1·min?1, p ? 0.001), and C (44.7 ± 5.4, ml·kg?1·min?1, p ? 0.001). Muscle buffer capacity was increased after altitude exposure in both groups with no differences between the groups (A, p ? 0.01; C, p = 0.06; altitude vs. baseline values), whereas the activity of the mitochondrial enzymes citrate synthase and 3-hydroxyl-CoA-dehydrogenase remained unchanged. In conclusion, VO2max was restored to baseline values after 6 weeks at 2800 m and muscle buffer capacity was improved in both moderately trained athletes and in inactive controls, suggesting that exercise does not affect the acclimatization process.
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