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Updated: Jul 3, 2026
Supramaximal Intensity Hypoxic Exercise and Vascular Function Assessment in Mice
Published on: March 15, 2019
Effects of normobaric hypoxia and hyperthermia on ventilatory responses to high-intensity interval training bouts
Michele Girardi1,2, Andrea Nicolò3, Samuele M Marcora4,5
1Department of Movement, Human and Health Sciences, University of Rome "Foro Italico", Piazza Lauro De Bosis 6, 00135, Rome, Italy.
Purpose:
Respiratory frequency (fR) and tidal volume (VT) show distinct responses during high-intensity interval training (HIIT) bouts, yet the underlying mechanisms remain unclear. We investigated the effects of hypoxia and hyperthermia on ventilatory responses to HIIT bouts.
Methods:
Ten recreationally trained males (mean ± SD: peak oxygen uptake: 3.98 ± 0.62 L/min, age: 28 ± 6 years) performed the same HIIT protocol to exhaustion in three randomized conditions: normobaric hypoxia (HYP, 15% O2), hyperthermia (HOT, 35 °C, 40% humidity), and control (CON, 18 °C and 40% humidity). Work-recovery phases (30-30 s) were performed at 109% of peak power output from a prior incremental test and 50 W, respectively.
Results:
Time-to-exhaustion (TTE) differed (P < 0.05) across CON (18.0 ± 4.4 min), HYP (9.4 ± 2.8 min), and HOT (12.6 ± 3.1 min) conditions. Iso-time fR was associated with changes in TTE and positively correlated with perceived exertion (P < 0.001; r = 0.85) and aural temperature (P < 0.001; r = 0.58). On average, fR increased during the work phase and decreased during recovery, primarily driving pulmonary ventilation ([Formula: see text]) during work-recovery alternations. Conversely, VT showed a smaller and opposite response, with higher values during recovery. VT plateaued in all conditions, but higher values were observed in HYP versus CON and HOT, accompanied by higher capillary blood lactate levels and lower blood oxygen saturation.
Conclusions:
fR is associated with changes in exercise tolerance irrespective of the environmental conditions tested and is more closely related to perceived exertion than to aural temperature. fR primarily drives the [Formula: see text] response to high-intensity work-recovery alternations, while VT appears fine-tuned on fR levels and the magnitude of metabolic inputs.
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