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Article en anglais, remerciements en français, résumés et conclusion en français et en anglais.; Factors underlying the amplitude of exercise performance reduction at altitude and the development of high-altitude illnesses are incompletely understood. To better describe these mechanisms, we assessed cardiorespiratory and tissue oxygenation responses to hypoxia in elite high altitude climbers. Eleven high-altitude climbers were matched with eleven non-climber trained controls according to gender, age and fitness level (maximal oxygen consumption, VO2max). Subjects performed two maximal incremental cycling tests, in normoxia and in hypoxia (inspiratory oxygen fraction: 0.12). Cardiorespiratory measurements and tissue (cerebral and muscle) oxygenation were assessed continuously. Hypoxic ventilatory and cardiac responses were determined at rest and during exercise; hypercapnic ventilatory response was determined at rest. During maximal exercise in hypoxia, climbers exhibited similar reductions than controls in VO2max (climbers -39±7%, controls -39±9%), maximal power output (climbers -27±5%, controls -26±4%) and SpO2. However, climbers had lower hypoxic ventilatory response during exercise (climbers 1.7±0.5, controls 2.6±0.7 L·min-1·%-1; p |
