Changes in the Prefrontal Cortex Oxygenation Levels During Cycling in the Supine and Upright Positions

The purpose of this study was to compare the prefrontal cortex (PFC) oxyhaemoglobin (HbO₂) levels observed during cycling in the upright and supine positions. Twelve healthy volunteers were randomly assigned to either the upright or supine position. After measuring maximal oxygen consumption (VO₂max) with a cycle ergometer in the upright position, each subject exercised at an intensity corresponding to 50% of the VO₂max for 20 min. HbO₂ levels in the right PFC (R-PFC) and left PFC (L-PFC) were measured using near-infrared spectroscopy. The R-PFC HbO₂ level measured within the 6-20-min window in the supine position was significantly higher than that in the upright position (0.072 ± 0.015 vs. 0.038 ± 0.013 mM·cm, respectively; p < 0.01). No significant effects were observed in the L-PFC. The laterality index for the supine position was significantly higher than that for the upright position (0.385 ± 0.181 vs. -0.272 ± 0.271, respectively; p < 0.05). Our results suggest that moderate-intensity cycling in the supine position increases R-PFC oxygenation.