Effect of acute hypoxia on maximal oxygen uptake and maximal performance during leg and upper-body exercise in Nordic combined skiers

We examined the effect of normobaric hypoxia (3200m) on maximal oxygen uptake (VO2max) and maximal power output (P-max) during leg and upper-body exercise to identify functional and structural correlates of the variability in the decrement of VO2max (Delta VO2max) and of maximal power output (Delta P-max). 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 in. deltoideus. 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 Delta VO2max nor for Delta P-max. Furthermore, no relationship was observed between individual Delta VO2max and Delta P-m, Analysis of structural data of m. deltoideus revealed a significant correlation between capillary density and Delta P-max (R=-0.80, p=0.03), as well as between volume density of mitochondria and Delta P-max (R = - 0.75, p = 0.05). In conclusion, it seems that VO2max and Pm,x 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.