Laterality of cortical oxygenation in the prefrontal cortex during 20 min of moderate-intensity cycling exercise: A near-infrared spectroscopy study

Introduction/Background Exercise therapy is a core component of rehabilitation for patients with cardiopulmonary disease and diabetes. A recent study showed that cognitive function improved after a single episode of moderate-intensity exercise. However, the laterality of cortical oxyhemoglobin (O 2 Hb) increases during exercise is unknown. We aimed to evaluate the laterality of O 2 Hb changes in the prefrontal cortex (PFC) during 20 min of moderate-intensity cycling exercise. Material and method Twelve healthy volunteers (9 women) participated. After a 3 min of rest, 20 min of exercise was performed at a workload of 50% VO 2peak , followed by 15 min of post-exercise rest. The O 2 Hb levels in the right (R-PFC) and left (L-PFC) prefrontal cortices were measured using a 34-channel, near-infrared spectrometry system. The O 2 Hb levels in each area were expressed as changes from the mean pre-exercise rest phase values. The O 2 Hb values in the last 5 min of the 20-min exercise period were averaged in both regions. The laterality index (LI) was calculated using the formula (L-PFC O 2 Hb–R-PFC O 2 Hb)/(L-PFC O 2 Hb + R-PFC O 2 Hb). A positive LI indicated that the increase in O 2 Hb in the L-PFC was larger than in the R-PFC; a negative LI indicated the opposite. Results O 2 Hb levels increased during the first 10 min and were maintained over the latter half of the exercise period in both R-PFC and L-PFC. The average O 2 Hb values in the last 5 min were 0.066 ± 0.013 mM·cm in the R-PFC and 0.085 ± 0.015 mM·cm in the L-PFC. The average LI of the PFC was 0.16 ± 0.10. Conclusion L-PFC-dominant O 2 Hb increases were observed during 20 min of moderate-intensity cycling exercises. The L-PFC plays an important role in executive functions and verbal working memory, which might be promoted by 20 min of exercise.