Pre-acclimation to exercise in normobaric hypoxia

摘要

Training in normobaric hypoxia prior to ascent to high altitude has been shown to induce acclimation to altitude in mountaineers. It is therefore likely that a similar training paradigm will be useful for athletes travelling to moderate altitude for training or competition. To test this contention, the acute effects of normobaric hypoxia upon selected physiological and performance parameters during treadmill exercise were examined. The parameters chosen were heart rate, blood lactate concentration, ventilation, oxyhaemoglobin saturation, and 5-km treadmill time-trial performance. The participants were 12 endurance-trained athletes (mean age 29.4 years, s=5.3; stature 1.80 m, s=0.8; body mass 78.3 kg, s=9.6). Tests were conducted once in sham conditions (F_IO₂=0.209, P_IO₂=159 mmHg, sea level; ST trial) and once in normobaric hypoxic conditions (F_IO₂=0.149, P_IO₂=85 mmHg, ∼2500 m; HT1 trial) using a normobaric hypoxic chamber system. Subsequently, the participants were assigned to two groups to train (75 min·day-1, 8 days, at a running speed corresponding to ≤2 mmol·l-1) in normobaric hypoxia (F_IO₂=0.149; n=6, hypoxia group) or sham conditions (F_IO₂=0.209; n=6, sham group). Acutely (ST vs. HT1), 5-km time-trial performance time was significantly extended in HT1 (13.6%, range 6.3-22.5%; P<0.01). Following training (HT2), performance improved by 0.8% and 2.3% for the sham and hypoxia training group respectively, but the improvement was not significant for either group (P>0.05). The individual data showed wide heterogeneity. In conclusion, aerobic training in normobaric hypoxia for 75 min·day-1 for 8 days does not enhance performance in hypoxia. However, due to the heterogeneity of response, it is evident that it may be effective at improving performance in hypoxia in some individuals.