“Sleep High - Train Low” Exerts Adaptative Effects On Ventilatory Response To Moderate Endurance Exercise

Abstract

PURPOSE This study determined whether repeated exposure to hypoxia in terms of sleep high - train low (SH) leads to adaptive changes in aerobic capacity, aerobic performance and the ventilatory response to exercise. METHODS Six non-altitude acclimated runners (H) spent 20 consecutive nights (10h/night) in normobaric hypoxia (FiO2 13.8%, corresponding to an altitude of 3300 above SL), whilst 6 control athletes (C) with similar training regimens slept under normoxic conditions. Before and after SH, a ramp test and an incremental exercise test on the treadmill were performed to determine maximum oxygen consumption (VO2max), maximum ventilation (VEmax) and running velocity at the individual anaerobic threshold (IAT), respectively. Before and after SH, the subjects additionally participated in a 15 min treadmill run (constant running velocity 75% IAT) in normoxia (CR-N), which was followed by an identical run in acute hypoxia (CR-H, FiO2 15.3%). RESULTS In H, oxygen saturation averaged 89.2 ± 2.4% at night. VO2max (before 66.6 ± 4.7/after 63,6 ± 4.9 ml/min/kg), VEmax (158.0 ± 18.3/159.0 ± 24.0 l) and IAT (17.1 ± 1.0/17.0 ± 1.5 km/h) were not affected by SH. In contrast, ventilation during CR-N (72.6 ± 12.7/78.9 ± 12.8 l) and CR-H (83.7 ± 14.9/90.7 ± 15.1 l) was significantly (p<0.05) higher after SH. This finding was not apparent in C. During CR-H, adaptation of ventilation to SH was paralleled by higher partial oxygen pressures (52.0 ± 5.8/57.3 ± 3.1 mmHg) and lower blood lactate concentrations (1.92 ± 0.36/1.34 ± 0.37 mmol/l) with no concomitant changes in C. CONCLUSIONS Passive exposure to repeated hypoxia as performed in the present study does not augment aerobic capacity, aerobic performance or maximal ventilation in endurance-trained athletes. However, SH enhances ventilatory response to moderate endurance exercise in normoxia as well as in hypoxia. This adaptive effect of SH is paralleled by a lower degree of hypoxemia and lower lactate concentrations if endurance exercise is performed in hypoxia. Thus, SH may be advantageous in acclimation to moderate endurance exercise at altitude. Supported by the Institut für Sportwissenschaft, Bonn, Germany