We examined whether skin-gas NO concentrations on the surface of damaging muscle would be a useful index for muscle damage or not. Seven healthy male students volunteered as the subjects, and none of them performed muscle damaging exercise at least within six months. The subjects performed 8 sets of 15 repetition maximum (RM) knee flexion-extension exercise consisting of predominantly isokinetic eccentric contraction. The skin-gas samples were obtained from the surface on belly muscle of rectus femoris before exercise and 1, 2, 3, 7days after exercise. The skin-gas NO concentration was measured by a chemiluminescence analyzer. Knee extension muscle strength (1RM), circumference of thigh, muscle soreness (visual analog scale; VAS), leukocytes, and serum creatine kinase activity were also measured.
　The skin-gas NO concentration significantly increased 2days after the exercise compared to pre-exercise values (p<0.01), and returned to pre-exercise levels 7days after exercise. The peak skin-gas NO concentration of each subject was about 1.4 times more than pre-exercise value, and that was significantly higher than the preexercise value. Although no significant difference was found in circumference of thigh during experimental period, muscle strength significantly (p<0.05) decreased, and VAS significantly (p<0.05) increased compared to the pre-exercise values after 1-3 days after exercise. Total leukocytes and neutrophils significantly (p<0.01) increased at 7days after exercise, and basophils significantly increased at 2 (p<0.05), 3, 7 (p<0.01) days after exercise compared to the pre-exercise values, however, there was no significant difference in eosinophils, monocytes, lymphocytes during experimental period. Serum CK activity increased significantly at 3 days after exercise compared to pre-exercise values (p<0.05), and returned to re-exercise levels 7days after exercise.
　These results suggest that the skin-gas NO concentrations on the surface of damaging muscle may be a useful index for decreasing muscle strength and muscle soreness.

DESCENTE SPORTS SCIENCE Vol.31/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE