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?
Does the fraction of inspired oxygen affect the NIRS-derived deoxygenated hemoglobin breakpoint during ramp-incremental exercise in physically active males?
The deoxygenated hemoglobin breakpoint response during exercise is not dependent on O2 driving pressure, suggesting other physiological mechanisms determine its occurrence.
Answers are grounded in this paper and cite their sources.
Hypoxia lowers the deoxygenated hemoglobin breakpoint while hyperoxia does not; leaves open non-O2 mechanisms in active males.
During ramp-incremental (RI) exercise to exhaustion, the near-infrared spectroscopy-derived deoxygenated hemoglobin ([HHb]) signal in the vastus lateralis muscle shows a linear increase up to a point at which a plateau-like response is manifested ([HHb] bp ). This study investigated if 1) the [HHb] bp is affected by different fractions of inspired O 2 ([Formula: see text]) [hypoxia (16%; HYPO); normoxia (21%; NORM); hyperoxia (30%; HYPER)]; and 2) an abrupt change to hyperoxic-inspired gas just before the occurrence of the [HHb] bp (HYPER SWITCH ) would affect the [HHb] plateau-like response. Ten physically active male participants reported to the laboratory on four separate occasions to perform an RI test to exhaustion in NORM, HYPO, and HYPER and an RI test to exhaustion with an abrupt increase in [Formula: see text] (30%; HYPER SWITCH ) 15 W before the power output (PO) associated with [HHb] bp in normoxia. PO, [HHb], tissue O 2 ([Formula: see text]), and pulse O 2 saturation ([Formula: see text]) were recorded continuously. Peak PO was significantly lower in HYPO (290 ± 21 W) and higher in HYPER (321 ± 22 W) and HYPER SWITCH (320 ± 19 W) compared with NORM (311 ± 18 W). The PO associated with [HHb] bp was not different between NORM and HYPER (246 ± 23 vs. 247 ± 24 W), but it was lower in HYPO (198 ± 31 W) than NORM and HYPER. The PO associated with the [HHb] bp in HYPER SWITCH (240 ± 23) was not different compared with NORM. HYPER and HYPER SWITCH resulted in greater [Formula: see text] and [Formula: see text] compared with NORM. These results suggest that the [HHb] bp response is not dependent of O 2 driving pressure and that other physiological mechanisms might determine its occurrence.
No takes yet. Share an insight, caveat, or question.
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.
Synapse has enriched 10 related papers. Consider them for comparative context: