Author(s): FAULHABER, M., Institution: UNIVERSITY INNSBRUCK, Country: AUSTRIA, Abstract-ID: 1278

INTRODUCTION:
Exposures to high altitude are associated with a decrease in aerobic endurance performance. Continuous exposures to high altitude improve aerobic endurance per-formance at high altitude. Alternatively, preacclimatization strategies, applying extended hypoxic exposures, have shown beneficial effects on aerobic endurance performance. However, scientific studies on more time-efficient preacclimatization programs are scarce although such strategies are more practicable. Therefore, the present project aimed to evaluate the effects of a time-efficient preacclimatization protocol on endurance performance during a subsequent acute high-altitude exposure.
METHODS:
Eighteen healthy individuals conducted three maximal 5-minute cycling time trials (TT). The first and second TT were completed in normoxia (Innsbruck 590 m, Aus-tria), whereas the first TT served for habituation and was not included to the analyses. The third TT was conducted in acute hypoxic conditions (Jungfraujoch 3450 m, Switzerland). After the first TT the subjects were allocated to the intervention (INT) or the control group (CON). Participants of the INT completed three to four passive sessions in a hypoxic chamber at a simulated altitude of 4300 m for preacclimatization. Each session lasted three to five hours with a cumulative exposure time of 16 hours for each participant. The participants of the CON had no exposure in the hypoxic chamber. A tow-way ANOVA for repeated measures (group x condition) was applied for statistical analysis.
RESULTS:
Mean power output during the TT in hypoxia decreased in both groups compared to normoxia. However, changes from normoxia to hypoxia were not significant be-tween groups (INT: 269 ± 77 to 223 ± 55 W, CON: 300 ± 68 to 255 ± 48 W, p = 0.847). In accordance, peak oxygen uptake during the TT decreased from 56.6 ± 7.1 to 46.9 ± 5.3 mL/min/kg in the INT and from 58.9 ± 8.1 to 49.0 ± 5.1 mL/min/kg in the CON (p = 0.951 between groups). Maximal heart rate decreased from 191.0 ± .6.2 to 187.7 ± 8.1 bpm in the INT and from 185.4 ± 11.8 to 182.9 ± 12.3 bpm in the CON (p = 0.751 between groups).
CONCLUSION:
The present study shows the expected altitude-related changes in aerobic endurance performance. However, results don’t indicate between-group differences in the changes from normoxia to hypoxia. Therefore, the applied preacclimatization program seems not to elicit beneficial effects for endurance performance during a sub-sequent acute altitude exposure. The diverging results compared to previous studies may be caused by a shorter total exposure time during preacclimatization in the present study. Furthermore, the application of normobaric hypoxia in this experiment compared to hypobaric hypoxia might results in reduced and/or less favourable adaptations.