Acute Low-Dose Hyperoxia during a Single Bout of High-Intensity Interval Exercise Does Not Affect Red Blood Cell Deformability and Muscle Oxygenation in Trained Men-A Randomized Crossover Study

Recent technological developments provide easy access to use an artificial oxygen supply (hyperoxia) during exercise training. The aim of this study was to assess the efficacy of a commercially available oxygen compressor inducing low-dose hyperoxia, on limiting factors of endurance performance. Thirteen active men (age 24 +/- 3 years) performed a high-intensity interval exercise (HIIE) session (5 x 3 min at 80% of W-max, separated by 2 min at 40% W-max) on a cycle ergometer, both in hyperoxia (4 L center dot min(-1), 94% O-2, HYP) or ambient conditions (21% O-2, NORM) in randomized order. The primary outcome was defined as red blood cell deformability (RBC-D), while our secondary interest included changes in muscle oxygenation. RBC-D was expressed by the ratio of shear stress at half-maximal deformation (SS1/(2)) and maximal deformability (EImax) and muscle oxygenation of the rectus femoris muscle was assessed by near-infrared spectroscopy. No statistically significant changes occurred in SS1/(2) and EImax in either condition. The ratio of SS1/(2) to EImax statistically decreased in NORM (p < 0.01; Delta: -0.10; 95%CI: -0.22, 0.02) but not HYP (p > 0.05; Delta: -0.16; 95%CI: -0.23, -0.08). Muscle oxygenation remained unchanged. This study showed that low-dose hyperoxia during HIIE using a commercially available device with a flow rate of only 4 L center dot min(-1) may not be sufficient to induce acute ergogenic effects compared to normoxic conditions.