We examined the effect of normobaric hypoxia (3200 m) on maximal oxygen uptake (V·O2max) and maximal power output (Pmax) during leg and upper-body exercise to identify functional and structural correlates of the variability in the decrement of V·O2max (DeltaV·O2max) and of maximal power output (DeltaPmax). Seven well trained male Nordic combined skiers performed incremental exercise tests to exhaustion on a cycle ergometer (leg exercise) and on a custom built doublepoling ergometer for cross-country skiing (upper-body exercise). Tests were carried out in normoxia (560 m) and normobaric hypoxia (3200 m); biopsies were taken from m. deltoideus. DeltaV·O2max was not significantly different between leg (- 9.1 ± 4.9 %) and upper-body exercise (- 7.9 ± 5.8 %). By contrast, Pmax was significantly more reduced during leg exercise (- 17.3 ± 3.3 %) than during upper-body exercise (- 9.6 ± 6.4 %, p < 0.05). Correlation analysis did not reveal any significant relationship between leg and upper-body exercise neither for DeltaV·O2max nor for DeltaPmax. Furthermore, no relationship was observed between individual DeltaV·O2max and DeltaPmax. Analysis of structural data of m. deltoideus revealed a significant correlation between capillary density and DeltaPmax (R = - 0.80, p = 0.03), as well as between volume density of mitochondria and DeltaPmax (R = - 0.75, p = 0.05). In conclusion, it seems that V·O2max and Pmax are differently affected by hypoxia. The ability to tolerate hypoxia is a characteristic of the individual depending in part on the exercise mode. We present evidence that athletes with a high capillarity and a high muscular oxidative capacity are more sensitive to hypoxia.
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