The purpose of present study was to compare the activated cross-sectional area (CSA) within quadriceps femoris (QF) between subjects with ACL lesion and those of normal subjects. Previously, we hypothesized that hindrance of afferent feedback from anterior cruciate ligament (ACL) could reduce the recruitment of motor units. Since the neuromuscular control such as the recruitment order of motor units were different depended on type of muscle contraction, the activated cross-sectional area (CSA) within the QF of patients with ACL lesion must be affected bilaterally. Six patients (5 male, 1 female) with ruptured ACL, and six healthy volunteers (4 male, 2 female) without a history of knee injury were enrolled in the present study. Since the both legs (injured and uninjured sides) of the patients with ACL lesion was compared with those of normal subjects, there were three experimental groups in this study; Injured side group, uninjured side group, and normal group. Two kinds of exercise-task (Eccentric task and Concentric task) were imposed to all subjects. They performed four sets of 15 repetitions of a knee extension exercise. The %-activated CSA were compared among groups on each exercisetask. We assume that each exercise-task would induce different response on the %-activated CSA of each experimental group. However, the result of present study indicated that there was no significant difference among the groups.

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