Peak Oxygen Intake and Hypoxia: Influence of Physical Fitness

Abstract

Eight men and eight women each performed peak oxygen intake tests on a cycle ergometer breathing ambient air and a mixture of 12% oxygen in nitrogen (equivalent to an altitude of 4400 m) in the two experiments. Hypoxia induced an average 28% decrease of peak oxygen intake, with a somewhat smaller decrease of power output. There were also small decreases in peak heart rate, peak blood pressure, peak ventilation, and peak blood lactate concentration. The major part of the impairment in oxygen transport was due to a reduction of arterial oxygen saturation, with small contributions from the decrease in heart rate and the decrease of ventilation. Subjects in good physical condition suffered a larger decrement of oxygen transport than their more sedentary colleagues, probably due to an unfavorable ratio of peak diffusing capacity to peak cardiac output. However, in the short term, this handicap could be countered by hyperventilation, and such a tactic could probably improve athletic performance over moderate distances.

Decrease in peak heart rate with acute hypoxia in relation to sea level V?O2max

“…The discrepancy between authors reporting a decrease in HR Peak in acute hypoxia (Benoit et al 1995;Martin and O'Kroy 1993;Roach et al 1996;Shephard et al 1988) and those observing no change (Fagraeus et al 1973;Lawler et al 1988;Wagner et al 1979) could be explained by the difference in the altitude used. Our team (Benoit et al 1995), Martin and O'Kroy (1993), Roach et al (1996) and Shephard et al (1988) used an altitude higher than 3800 m whereas Lawler et al (1988), Fagraeus et al(1973), andWagner et al (1979) used an altitude lower than 3800 m. Studies which reported an effect of altitude on HR peak were carried out at simulated altitudes higher than 4000 m. Martin's study was carried out at 3800 m and demonstrated a decrease in HR peak only for trained subjects with a low SaO 2 . The decrement in HR peak is statistically significant at equivalent altitudes of 3800 m up to 5400 m. The progressive reduction in HR peak with altitude observed in the present study is in agreement with the previous study of Lundby et al (2001).…”

“…The situation is less clear in acute hypoxia. While several authors reported a decrease in HR peak in acute hypoxia (Benoit et al 1995;Lundby et al 2001;Martin and O'Kroy 1993;Roach et al 1996;Shephard et al 1988), others observed no change (Cerretelli 1980;Hughes et al 1968;Lawler et al 1988;Wagner et al 1979). These conflicting results might result from different arterial oxygen saturation levels (SaO 2 ) subsequent to the different altitudes studied.…”

Peak Heart Rates at Extreme Altitudes

“…Everest (Cymerman et al, 1989). Since the subjects in the present study and those in OEII had approximately the same sea-level maximal heart rates and only a slightly different sealevel VO 2 max , one would predict similar reductions in maximal heart rate at equivalent decreases in barometric pressure (Grover et al, 1967;Kjaer et al, 1988;Shephard et al, 1988;Martin and O'Kroy, 1993). West has suggested that the acclimatization process may account for these differences among the results of field studies and those of hypobaric chamber experiments (West, 1998).…”

Methods to Estimate V˙O2max upon Acute Hypoxia Exposure

“…Furthermore, we also examined the predictive utility of these models by comparing the predictions of our models to a dataset of 74 participants obtained from a subset of studies in the meta-analysis (3,7,16,26,28,36,37,39) that reported participant-level data. Scores for individual participants are fundamentally different from group-level data in the metaanalysis.…”