EMG PROFILES OF ACL-DEFICIENT PATIENTS DURING WALKING - THE INFLUENCEOF MILD FATIGUE

The purpose of this study was to determine muscle activities after ACL rupture during walking and running and to investigate the influence o f mild fatigue (10 min walking) on these activities. A group of 12 pat ients with ACL-ruptures was compared with a control group (healthy vol unteers) of 15 persons. Linear envelopes of EMG-activity from vastus m edialis, vastus lateralis, biceps femoris and medial hamstrings were m easured. Patients and control persons walked on a treadmill at speeds of 1.2 m/s (samples at t = 2 min and t = 12 min) and 2.8 m/s i.e. runn ing (sample at t = 15 min). The patient group showed significantly low er muscle activities of vastus lateralis (p < 0.001) and medial hamstr ings (p < 0.05) for both the injured and uninjured leg during running compared to the control group. After 10 minutes walking, the mean-EMG of biceps femoris (p < 0.05) and medial hamstrings (p < 0.01) decrease d as did the activity time of biceps femoris (p < 0.05), medial hamstr ings (p < 0.01) and vastus medialis (p < 0.001) for the injured leg of the patient group. Control persons showed no significant changes. Thu s, mild fatigue did effect only the EMG-pattern of the patients. Patie nts with ACL-ruptures should be trained not only on strength and stabi lisation, but also on endurance. A decrease in hamstrings activity dur ing walking might be a sensitive measure for evaluation of the rehabil itation process, as those muscles may be able to substitute ACL-defici ency.