This study set out to determine the effects of different inspired oxygen fractions on repeated sprint performance and cardiorespiratory and neuromuscular responses, to construct a hypoxic dose response.
Nine male, well trained multi sport athletes completed 10×6 all-out run sprints with 30s recovery in 5 conditions of differing O2 saturation: 12%, 13%, 14%, 15% and 21%.
Peak running was measured in each sprint and EMG data was recorded from the m. vastus lateralis alongside heart rate and blood oxygen saturation. Cardiorespiratory response was assessed via breath by breath expired air analysis and muscle oxygen status was evaluated via near infrared spectroscopy.
Results: In parallel with the higher heart rate, minute ventilation, blood lactate concentration and muscle deoxygenation; lower blood oxygen saturation, pulmonary oxygen uptake and integrated EMG were registered in all conditions, with the greatest changes from baseline observed during the 13% trial. However, fatigue index and speed decrement were significantly greater only during the 12% vs 21% trial.
The study concluded that physiological responses associated with performance 10 x 6s sprints interspersed with 30s passive recovery was incrementally greater as oxygen levels decreased to 13%, yet fatigue development was exacerbated relative to normoxia (oxygen 21% sea level) only at the 12% oxygen.
This study suggests that sprint intervals were slower in hypoxia, but physiological performance gains were regconised.