Effects Of Different Levels Of Hypoxia On Anaerobic Energy Release During Supramaximal Exercise In Trained Athletes

Abstract

It has been suggested that supramaximal exercise under normobaric hypoxia results in greater anaerobic energy release compared to normoxia. However, the effects of different levels of hypoxia on anaerobic energy release during supramaximal exercise remain unclear. PURPOSE The purpose of the present study was to investigate the effects of different levels of hypoxia on anaerobic energy release during supramaximal exercise. METHODS The present study was approved by Juntendo University Human Ethics Committee. Seven male subjects volunteered to participate in the present study [age; 20±1 (mean±SD) years, height; 170±6cm, weight; 65.3±6.5kg, peak oxygen uptake; 56.5±3.8ml-kg−1-min−1]. All subjects performed 12 submaximal cycling economy tests to establish the relationship between submaximal workload and O2 uptake. Following this, subjects performed three 40 seconds of Wingate tests under 20.9, 16.4 and 12.8%O2conditions. During the Wingate tests, pedal frequency, power output and breath-by-breath O2 uptake were measured and averaged every 10 seconds. O2 demand, O2 deficit and %anaerobic energy release were estimated according to the method of Calbet et al. (2003). RESULTS No significant differences were observed in pedal frequency, power output and estimated O2 demand in each interval of 10 seconds among three O2conditions. O2 uptake in 12.8%O2 condition was significantly lower in the intervals of 21∼30 seconds (20.9%O2; 9.6±3.2, 16.4%O2; 7.4±1.6, 12.8%O2; 5.3±2.5ml-kg−1-10sec−1)! and 31∼40 seconds (20.9%O2; 10.6±3.7, 16.4%O2; 7.6±2.8, 12.8%O2; 6.7±3.5ml-kg-10sec−1) compared to 20.9%O2 condition (P <0.01 and 0.05, respectively). O2deficit in 12.8%O condition was significantly lower in the interval of 21∼30 seconds (20.9%O2; 7.2±3.0, 16.4%O2; 9.2±1.9, 12.8%O2; 10.9±2.3ml-kg−1-10sec−1) compared to 20.9%O2 condition (P <0.01). %anaerobic energy release in 12.8%O2 condition was significantly higher in the intervals of 21∼30 seconds (20.9%O2; 43.0±19.0, 16.4%O2; 55.3±9.5, 12.8%O2;67.6±14.5%) and 31∼40 seconds (20.9%O2; 17.4±30.1, 16.4%O2; 39.1±21.8, 12.8%O2; 45.4±23.0%) compared to 20.9 %O2 condition (bothP <0.01). CONCLUSION Severe hypoxia induced a significant increase of hypoxia-induced anaerobic energy release during supuramaximal exercise. This suggests that there may be a threshold of O2 concentration that provides a significant increase of anaerobic energy release during supramaximal exercise under hypoxia.