The purpose of this study was to investigate the usage of the lower limb muscles (quadriceps femoris : QF, m. vastus lateralis : VL, m. rectus lemons : RF, m. vastus medialis : VM, m. vastus intermidialis : VI, hamstring : HM, m. gastrocnemius : UN, tihialis anterior : TA) and blood lactic acid concentration during uphill ( : UR +5 %) and downhill running ( : DR - 5 %) . We used magnetic resonance imaging (MRI) as one of the major indices. Seven healthy male volunteers participated in this study. T 2-weighted MR imaging, muscle surface temperature and blood lactic acid concentration were measured before and after UR and DR. In MRI imaging, the T2 value was defined as the area in which a high signal appeared after exercise.
The value of the blood lactic acid concentration of UR was higher than that of DR (p<0.001) . After DR, the muscle surface temperature of RF was lower in comparison with other muscles (p< 0.05) . After UR, the T2 value of RF (p<0.05), HM (p<0.01) and UN (p<0.05) was higher than after DR exercise. During UR, a positive correlation (r=0.818) existed between the T 2 value of GN and blood lactic acid concentration (P<0.05) . During DR, a positive correlation (r=0.739) was also observed between the T 2 value of QF and blood lactic acid concentration (p<0.05) .
From these results, we conclude that (1) the pattern of usage of lower limb muscles differs during UR and DR, (2) the most mobilized muscles in the lower limbs for UR are GN and HM, and (3) the most mobilized muscle in the lower limbs for DR is QF, respectively. These findings show that different exercises affect the blood lactic acid concentration differently.

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.
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.