The purpose of the study was to investigate the effects of hypoxia responses during moderate- and severe-intensity exercise performed to exhaustion. Nine healthy university students, five men, and four women (mean ± SD, age, 23 ± 1 y; height 167 ± 8 cm; weight 73 ± 7 kg) performed a cycle ergometer test in normoxia and hypoxia conditions. Cardiorespiratory, metabolic, and perceptual responses were measured during moderate-intensity and during severe-intensity exercise. During moderate-intensity exercise, hypoxia exaggerates the cardiorespiratory and ventilatory responses and delays the attainment of the steady state VO2 kinetics. However, during severe-intensity exercise, compensatory responses were not adequate, oxygen demand was slightly increased and VO2 max was reduced in hypoxia affecting the overall performance. Therefore, the greater reliance on the anaerobic pathways could have a serious implication on the performance of the exercise over a wide range of intensities.