The effects of acute normobaric hypoxia on standing balance while dual-tasking with and without visual input

To investigate the influence of acute normobaric hypoxia on standing balance under single and dual-task conditions, both with and without visual input.

20 participants (7 female, 20-31 years old) stood on a force plate for 16, 90-s trials across four balance conditions: single-task (quiet stance) or dual-task (auditory Stroop test), with eyes open or closed. Trials were divided into four oxygen conditions where the fraction of inspired oxygen (F_IO₂) was manipulated (normoxia: 0.21 and normobaric hypoxia: 0.16, 0.145 and 0.13 F_IO₂) to simulate altitudes of 1100, 3,400, 4300, and 5200 m. Participants breathed each F_IO₂ for ~ 3 min before testing, which lasted an additional 7-8 min per oxygen condition. Cardiorespiratory measures included heart rate, peripheral blood oxygen saturation, and pressure of end tidal (P_ET) CO₂ and O₂. Center of pressure measures included total path length, 95% ellipse area, and anteroposterior and mediolateral velocity. Auditory Stroop test performance was measured as response accuracy and latency.

Significant decreases in oxygen saturation and P_ETO₂, and increased heart rate were observed between normoxia and normobaric hypoxia (P < 0.0001). Total path length was higher at 0.13 compared to 0.21 F_IO₂ for the eyes closed no Stoop test condition (P = 0.0197). No other significant differences were observed.

These findings suggest that acute normobaric hypoxia has a minimal impact on standing balance and does not influence auditory Stroop test or dual-task performance. Further investigation with longer exposure is required to understand the impact and time course of normobaric hypoxia on standing balance.