Abstract
The aims of the present study were to clarify the differences in muscle oxygen dynamics between eccentric (ECC) and concentric (CON) contractions and to investigate the relationship between muscle oxygen dynamics and the pattern of skeletal muscle recruitment during ECC and CON contractions. Fifteen healthy male subjects (age 21.8 ± 2 yrs) performed isokinetic ECC and CON knee extension and flexion exercise for 1 min at an angular velocity of 180°/s. Changes in muscle oxygenation (MO) levels in the active muscle were measured using near-infrared spectroscopy (NIRS) whose probe was placed on the rectus femoris. Bipolar surface electrodes recorded the electromyogram (EMG) activity of this muscle. The MO levels during ECC contraction were significantly higher at 10 s and 15 s after the onset of exercise while MO levels during CON contraction were significantly higher 60 s following the onset of exercise. A significant correlation was indicated between MO levels and EMG activity during CON contraction (p<0.05). These results reveal that oxygen supply-consumption balance in ECC and CON contraction are different. Moreover, this suggests that muscle activity in CON contraction increases and the oxygen supply to active muscle may exceed the oxygen consumption in active muscle.