Key result
Exercise at 3800 m altitude with 25% O2 and 5.0% CO2 significantly increased heart rate and systolic blood pressure, with parasympathetic activity dominating cardiac autonomic modulation.
Why the study?
Does exercise in an oxygen-enriched environment with varying CO2 concentrations at high altitude alter cardiovascular responses (heart rate variability, heart rate, blood pressure) in human subjects?
Does exercise in an oxygen-enriched environment with varying CO2 concentrations at high altitude alter cardiovascular responses (heart rate variability, heart rate, blood pressure) in human subjects?
Exercise at high altitude with 25% oxygen and 5% carbon dioxide enrichment significantly increases heart rate and blood pressure while modulating autonomic tone toward parasympathetic dominance.
Does not support changing high-altitude exercise protocols; leaves open confirmation of autonomic effects in randomized trials.
BACKGROUND: This study explores the responses of the cardiovascular system as humans exercise in an oxygen-enriched room at high altitude under various concentrations of CO₂. METHODS: The study utilized a hypobaric chamber set to the following specifications: 3800 m altitude with 25% O₂ and different CO₂ concentrations of 0.5% (C1), 3.0% (C2) and 5.0% (C3). Subjects exercised for 3 min three times, separated by 30 min resting periods in the above-mentioned conditions, at sea level (SL) and at 3800 m altitude (HA). The changes of heart rate variability, heart rate and blood pressure were analyzed. RESULTS: Total power (TP) and high frequency power (HF) decreased notably during post-exercise at HA. HF increased prominently earlier the post-exercise period at 3800 m altitude with 25% O₂ and 5.0% CO₂ (C3), while low frequency power (LF) changed barely in all tests. The ratios of LF/HF were significantly higher during post-exercise in HA, and lower after high intensity exercise in C3. Heart rate and systolic blood pressure increased significantly in HA and C3. CONCLUSIONS: Parasympathetic activity dominated in cardiac autonomic modulation, and heart rate and blood pressure increased significantly after high intensity exercise in C3.
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Liu et al. (2015) studied this question. Exercise in hypobaric chamber at 3800 m altitude with 25% O2 and various CO2 concentrations vs. Sea level and 3800 m altitude without enrichment was evaluated on Changes in heart rate variability, heart rate, and blood pressure. Exercise at 3800 m altitude with 25% O2 and 5.0% CO2 significantly increased heart rate and systolic blood pressure, with parasympathetic activity dominating cardiac autonomic modulation.
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