| The purpose of this study was to measure EMG timing and amplitude characteristics of the vastus lateralis, vastus medialis, rectus femoris, medial and lateral hamstrings, and the medial and lateral heads of gastrocnemius muscle in subjects with an ACL-deficient knee, and to determine whether function level can be predicted from the EMG variables. Eleven subjects with a chronic, isolated ACL injury participated in this study. Subjects' level of function was quantified by ranking their performance on three functional tests. A combined score to reflect level of function was then calculated using the ranks from the three tests. Surface EMG was then recorded from the above muscles during two step-down tasks: stepping down and landing on the injured limb; and stepping down to the uninjured limb while weight bearing on the uninjured limb. Each task was divided into phases, and then onset latencies were determined and relative amplitudes established for each phase. An ensemble average profile of muscle activity was also calculated to describe qualitatively the patterns of muscle activity during each task. A multiple regression analysis was used to test the hypothesis that function level can be predicted using EMG characteristics from the major muscles around the knee. (Abstract shortened by UMI.)... |
