Effects of Acute Hypoxia on Lactate Thresholds and High-Intensity Endurance Performance-A Pilot Study

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.