Effect of muscle contraction type and speed on tissue oxygen dynamics in the M. vastus medialis during repeated knee extension exercise / 体力科学

ABSTRACT

The purpose of this study was to analyze the relationship between activity pattern and temporal changes in the oxygen dynamics of human femoral medial vastus muscles. Oxygen dynamics were evaluated from the surface of the body by near-infrared spectroscopy (NIRS) . Arterial occlusion tests were performed in the femoral region at a cuff pressure of 300 mmHg. Exercise type and speed were controlled by CYBEX 6000. The exercise types examined were concentric contraction (CON) and eccentric contraction (ECC) . The 3 angular velocities of 90, 120 and 180 degrees were used as the exercise speeds. Exercise was performed continuously 60 times at maximum effort. The subjects were 7 healthy males with a mean age of 19.6±0.5 years. A transient decrease in oxygen concentration was observed during circulatory occlusion ; and rapid hyperemia occurred immediately after the removal of pressure. Oxygen concentration peaked above the control level and then returned to the initial level. In the CON exercise, the initial decrease in oxygen concentration was the largest at CON 90, and a gradual increase in oxygen concentration was clearly observed during exercise. In the recovery stage, after exercise at CON 90, 120 and 180, oxygen concentration exceeded the control level before exercise, then peaked and returned to the initial level. In the ECC exercise, an initial decrease in oxygen concentration was similar to that in the CON exercise, but a gradual increase in oxygen concentration was not observed during the exercise ; nor did oxygen concentration exceed the control level in the recovery stage after the exercise.<BR>These results indicate that an increase in oxygen level after the removal of arterial occlusion, during and after the CON exercise was much higher than the control level before the exercise, sug-gesting the involvement of reactive hyperemia and exercise hyperemia.