Abstract
The present project compared acute hypoxia-induced changes in lactate thresholds (methods according to Mader, Dickhuth and Cheng) with changes in high-intensity endurance performance. Six healthy and well-trained volunteers conducted graded cycle ergometer tests in normoxia and in acute normobaric hypoxia (simulated altitude 3000 m) to determine power output at three lactate thresholds (P(Mader), P(Dickhuth), P(Cheng)). Subsequently, participants performed two maximal 30-min cycling time trials in normoxia (test 1 for habituation) and one in normobaric hypoxia to determine mean power output (P(mean)). P(Mader), P(Dickhuth) and P(Cheng) decreased significantly from normoxia to hypoxia by 18.9 ± 9.6%, 18.4 ± 7.3%, and 11.5 ± 6.0%, whereas P(mean) decreased by only 8.3 ± 1.6%. Correlation analyses revealed strong and significant correlations between P(mean) and P(Mader) (r = 0.935), P(Dickhuth) (r = 0.931) and P(Cheng) (r = 0.977) in normoxia and partly weaker significant correlations between P(mean) and P(Mader) (r = 0.941), P(Dickhuth) (r = 0.869) and P(Cheng) (r = 0.887) in hypoxia. P(Mader) and P(Cheng) did not significantly differ from P(mean) (p = 0.867 and p = 0.784) in normoxia, whereas this was only the case for P(Cheng) (p = 0.284) in hypoxia. Although investigated in a small and select sample, the results suggest a cautious application of lactate thresholds for exercise intensity prescription in hypoxia.