The purpose of the present study is to investigate the relationship between muscle force and blood volume and oxygenation in the sensorimotor cortex of the human brain by using multi-channel near infrared spectroscopy. Seven healthy men performed isometric knee extension at 10%, 40% and 60% of maximum voluntary contraction in a 5-sec of exertion with a 30-sec of recovery for ten repetitions. During the knee extension exercises, surface electromyography (mEMG activity) of the vastus lateralis and rectus femoris was measured. Multi-channel near infrared spectroscopy (Mch-NIRS) was applied to the top of the head for measuring oxygeneted hemoglobin (Oxy Hb) and deoxygenated hemoglobin (Deoxy Hb) and total hemogrobin (Total Hb) at the sensorimotor cortex of ipsilateral hemispheres. The kinetics of the Oxy Hb and Total Hb during isometric knee extension exercises were very similar, and no change were found in the Deoxy Hb during the exercises. There were significant relationships between muscle force and Total Hb (r=0.647, p<0.01) and Oxy Hb (r=0.647, p<0.01). We found significant correlation coefficient between mEMG activity of the vastus lateralis and Total Hb and Oxy Hb: r=0.699, p<0.01, and r=0.669, p<0.01, respectively; and that of the rectus femoris and Total Hb and Oxy Hb: r=0.665, p<0.01, and r=0.692, p<0.01, respectively. We concluded that motor-related cerebral cortex in human brain encoded muscle activation (muscle force and EMGs) during exercise as has been demonstrated by non-human primates.

DESCENTE SPORTS SCIENCE Vol.24/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE