Abstract: Purpose: This study investigated the response of the ventilatory threshold (VT) to acute normobaric hypoxia and compared the agreement between software-based algorithms which use automatic detection to identify the VT. Results were used to examine whether the VT can be used as a physiological parameter to prescribe and monitor exercise intensity in hypoxic exercise training programs. Methods: Fourteen untrained individuals (7 women, 7 men; age 22 ± 2 years, O2peak 46 ± 7 mL/kg.min) completed five identical graded exercise tests (randomized order) on a cycle ergometer to measure VT at sea-level (SL) and in response to four normobaric hypoxic conditions (FIO2: 0.185, 0.165, 0.142, 0.125) equivalent to 1,000, 2,000, 3,000 and 4,000 m. Data were analyzed using a one-way analysis of variance (ANOVA) with repeated measures. Results: The VT was similar across all conditions (SL = 1.98 ± 0.46, 1,000 m = 2.03 ± 0.61, 2,000 m = 2.27 ± 0.62, 3,000 m = 1.84 ± 0.50, 4,000 m = 2.29 ± 0.58 L/min) for all algorithms used despite a reduction in arterial oxygen saturation at 3,000 (P = 0.01) and 4,000 m (P = 0.01) compared with SL values. Conclusion: The VT appears to be a suitable physiological parameter for exercise prescription in normobaric hypoxia up to an altitude of 4,000 m.
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