Key result
Hypoxia lowered the power output associated with the deoxygenated hemoglobin breakpoint compared to normoxia (198 vs 246 W), whereas hyperoxia had no effect.
Why the study?
It was unknown whether the NIRS-derived deoxygenated hemoglobin breakpoint during ramp-incremental exercise is affected by different fractions of inspired O2 or an abrupt change to hyperoxic gas.
Does the fraction of inspired oxygen affect the NIRS-derived deoxygenated hemoglobin breakpoint during ramp-incremental exercise in physically active males?
Comparison
Ramp-incremental exercise in HYPO (16%), HYPER (30%), and HYPER SWITCH vs NORM (21%)
Design
Crossover physiological study
Authors
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Hypoxia lowers the deoxygenated hemoglobin breakpoint while hyperoxia does not; leaves open non-O2 mechanisms in active males.
Does the fraction of inspired oxygen affect the NIRS-derived deoxygenated hemoglobin breakpoint during ramp-incremental exercise in physically active males?
Absolute Event Rate: 198% vs 246%
The deoxygenated hemoglobin breakpoint response during exercise is not dependent on O2 driving pressure, suggesting other physiological mechanisms determine its occurrence.
Azevedo et al. (2019) studied Healthy physically active (n=10). Different fractions of inspired O2 (hypoxia, hyperoxia) vs. Normoxia (21% O2) was evaluated on Power output associated with the deoxygenated hemoglobin breakpoint ([HHb]bp). Hypoxia lowered the power output associated with the deoxygenated hemoglobin breakpoint compared to normoxia (198 vs 246 W), whereas hyperoxia had no effect.
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