Electromyography Evaluation of Bodyweight Exercise Progression in a Validated Anterior Cruciate Ligament Injury Rehabilitation Program: A Cross-Sectional Study

OBJECTIVES: Regaining muscle strength is essential for successful outcome after anterior cruciate ligament injury, why progression of exercise intensity in anterior cruciate ligament injury rehabilitation is important. Thus, this study evaluated hamstring and quadriceps muscle activity progression during bodyweight exercises used in a validated anterior cruciate ligament injury rehabilitation program. DESIGN: The study design involved single-occasion repeated measures in a randomized manner. Twenty healthy athletes (nine females) performed nine bodyweight exercises (three exercises per rehabilitation phase). Surface electromyography signals were recorded for hamstring (semitendinosus, biceps femoris) and quadriceps (vastus medialis, vastus lateralis) muscles and normalized to isometric peak electromyography. RESULTS: Hamstring muscle activity did not increase from one rehabilitation phase to the next, ranging between 8% and 45% normalized electromyography for semitendinosus and 11% and 54% normalized electromyography for biceps femoris. Only one exercise (Cook hip lift) exhibited hamstring muscle activities more than 60% normalized electromyography. By contrast, quadriceps muscle activity increased, and late-phase exercises displayed high normalized electromyography (vastus lateralis >60% and vastus medialis >90% normalized electromyography). CONCLUSIONS: The examined bodyweight exercises did not progress for hamstring muscle activity but successfully progressed for quadriceps muscles activity. This study highlights the need for consensus on exercise selection when targeting the hamstring muscles in the rehabilitation after anterior cruciate ligament injury.