ECCENTRIC KNEE FLEXOR TORQUE FOLLOWING ANTERIOR CRUCIATE LIGAMENT SURGERY

The purposes of this study were to compare eccentric knee flexor torqu e and muscle activation in the limbs of normal (NOR) subjects and in s ubjects who had undergone unilateral ACL autograft surgical reconstruc tion (INJ) and to assess the effect of movement speed on EMG/ torque r atios and eccentric-concentric actions. Fourteen subjects (7 NOR and 7 INJ) were tested for knee eccentric flexor torque and EMG activity at four isokinetic speeds (15 degrees, 30 degrees, 45 degrees, and 60 de grees . s(-1)). Results revealed that post-surgical limbs (ACL) produc ed significantly less (P < 0.05) eccentric torque and flexor EMG activ ity at 60 degrees . s(-1) than uninjured (UNI) contralateral limbs. Ec centric torque rose significantly as speed increased from 45 degrees t o 60 degrees . s(-1) for surgical group uninjured limbs and NOR group left and right limbs. Eccentric flexor torque increased with speed for both groups and approximated equality with concentric extensor torque at 60 degrees . s(-1) for INJ group ACL and UNI limbs. Concentric fle xor muscle EMG/torque ratios were 30-191% greater than eccentric muscl e actions across groups and speeds. The results suggest that ACL dysfu nction may result in reduced eccentric flexor torque at rapid movement speeds, that eccentric flexor torque increases with movement speed an d may have the capacity to counter forceful extensor concentric torque , and that eccentric muscle actions produce less muscle activation per unit force than concentric actions which may reflect reduced energy c ost.