Human motor cortex oxygenation measured by NIRS during ergometer exercise

Abstract

[Purpose] The aim of this study was to clarify the activity of the lower limb area of the sensory motor cortex during bicycle ergometer exercise at light loads using functional near infra-red spectrometry (fNIRS) and its relationship with exercise load as well as the temporal changes in cortex activity. [Subjects and Method] The subjects were 9 healthy adults. There were 4 exercise tasks of constant work and pedaling rates, and 2 tasks of changing the pedaling rate (but not work rate) during exercise. Each of the tasks were performed in 3 contiguous sets, and we examined and compared the changes in oxygenated hemoglobin (oxyHb) at 5-second intervals from the start of exercise. [Results] In the 4 tasks of constant work and pedaling rates, the change in oxyHb over 5~10 seconds from the start of exercise was significantly higher than over 0~5, 10~15 and 15~20 seconds, and the transient increase in oxyHb decreased despite the continuation of exercise. In the 2 tasks in which the pedaling rate was changed, we found that oxyHb gradually decreased after the initial increase at the start of exercise, but increased again with increase of the pedaling rate. [Conclusion] We revealed the activity of the lower limb area of the primary motor cortex during bicycle ergometer exercise. We also demonstrated that the effect of changing the pedaling rate during exercise is to increase the blood flow in the lower limb area of the primary motor cortex.