## Abstract

During exposure to altitudes greater than about 2200 m, maximal oxygen uptake ( {Mathematical expression}) is immediately diminished in proportion to the reduction in the partial pressure of oxygen in the inspired air. If the exposure lasts longer than a couple of days, an increase in arterial oxygen content (CaO_{2}), due to a hemoconcentration and an increase in arterial oxygen saturation, occurs. However, there is also a reduction in maximal cardiac output ( {Mathematical expression}) at altitude which offsets the increase in CaO_{2} and, therefore, {Mathematical expression} does not improve. The purpose of this investigation was to study the contribution of the increase in CaO_{2} to the working muscles without the potentially confounding problem of a reduced {Mathematical expression}. The approach used was to have seven male subjects (aged 17 to 24 years) perform one- and two-legged {Mathematical expression} tests on a cycle ergometer at sea level (SL, PIO_{2} = 159 Torr), after 1 h at 4300 m simulated altitude (SA, PIO_{2} = 94 Torr) and during two weeks of residence on the summit of Pikes Peak, CO. (pP, 4300 m, PIO_{2} = 94 Torr). Cardiac output limits maximal performance during two-legged cycling but does not limit performance during one-legged cycling. During the study, CaO_{2} changed from 189±3 (mean ±SE) at SL to 161±4 ml·L^{-1} during SA (SL vs. SA, p<0.01) and to 200±6 ml·L^{-1} at PP (SL vs. PP, p<0.05; SA vs. PP, p<0.01). Two-legged {Mathematical expression} decreased from 3.64±0.26 L·min^{-1} at SL to 2.70±0.14 L·min^{-1} during SA (p<0.01) to 2.86±0.16 L·min^{-1} at PP (p<0.01). One-legged {Mathematical expression} decreased from 2.95±0.22 at SL to 2.25±0.17 L·min^{-1} during SA (SL vs. SA, p<0.01) but improved to 2.66±0.18 L·min^{-1} at PP (SA vs. PP, p<0.05). Since only one-legged {Mathematical expression} increased as more oxygen was made available to the working muscles, the altitude-induced reduction in {Mathematical expression} can be implicated as being responsible for the reduction in {Mathematical expression} during two-legged cycling.

Original language | English |
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Pages (from-to) | 761-766 |

Number of pages | 6 |

Journal | European Journal of Applied Physiology and Occupational Physiology |

Volume | 57 |

Issue number | 6 |

DOIs | |

State | Published - 1 Nov 1988 |

## Keywords

- Altitude acclimatization
- Cardiac output
- Maximal oxygen consumption
- One-legged cycling