Enhanced O2 extraction fraction (≥90%) contributes to remarkably high maximal oxygen uptake in endurance-trained individuals, alongside linear increases in cardiac output and leg blood flow (P<0.001).
Meta-Analysis (n=388)
Enhanced oxygen extraction fraction (≥90%) significantly contributes to the high maximal oxygen uptake observed in endurance-trained individuals, alongside oxygen delivery.
Abstract We analysed the importance of systemic and peripheral arteriovenous O 2 difference ( difference and a‐v f O 2 difference, respectively) and O 2 extraction fraction for maximal oxygen uptake ( ). Fick law of diffusion and the Piiper and Scheid model were applied to investigate whether diffusion versus perfusion limitations vary with . Articles ( n = 17) publishing individual data ( n = 154) on , maximal cardiac output ( ; indicator‐dilution or the Fick method), difference (catheters or the Fick equation) and systemic O 2 extraction fraction were identified. For the peripheral responses, group‐mean data (articles: n = 27; subjects: n = 234) on leg blood flow (LBF; thermodilution), a‐v f O 2 difference and O 2 extraction fraction (arterial and femoral venous catheters) were obtained. and two‐LBF increased linearly by 4.9‐6.0 L · min –1 per 1 L · min –1 increase in ( R 2 = .73 and R 2 = .67, respectively; both P < .001). The difference increased from 118‐168 mL · L –1 from a of 2‐4.5 L · min –1 followed by a reduction (second‐order polynomial: R 2 = .27). After accounting for a hypoxemia‐induced decrease in arterial O 2 content with increasing ( R 2 = .17; P < .001), systemic O 2 extraction fraction increased up to ~90% ( : 4.5 L · min –1 ) with no further change (exponential decay model: R 2 = .42). Likewise, leg O 2 extraction fraction increased with to approach a maximal value of ~90‐95% ( R 2 = .83). Muscle O 2 diffusing capacity and the equilibration index Y increased linearly with ( R 2 = .77 and R 2 = .31, respectively; both P < .01), reflecting decreasing O 2 diffusional limitations and accentuating O 2 delivery limitations. In conclusion, although O 2 delivery is the main limiting factor to , enhanced O 2 extraction fraction (≥90%) contributes to the remarkably high in endurance‐trained individuals.
Skattebo et al. (Mon,) conducted a meta-analysis in Healthy young men (n=388). Enhanced O2 extraction fraction (≥90%) contributes to remarkably high maximal oxygen uptake in endurance-trained individuals, alongside linear increases in cardiac output and leg blood flow (P<0.001).