Regaining muscle strength is essential for successful outcome after anterior cruciate ligament (ACL) injury, why progression of exercise intensity in ACL injury rehabilitation is important. Thus, this study evaluated hamstring and quadriceps muscle activity progression during bodyweight exercises used in a validated ACL injury rehabilitation program.
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 EMG (nEMG).
Hamstring muscle activity did not increase from one rehabilitation phase to the next, ranging between 8-45% nEMG for semitendinosus and 11-54% nEMG for biceps femoris. Only one exercise (Cook hip lift) exhibited hamstring muscle activities above 60% nEMG. By contrast, quadriceps muscle activity increased, and late phase exercises displayed high nEMG (vastus lateralis >60% and vastus medialis >90% nEMG).
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 ACL injury.
This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.
1Department of Physiotherapy, Faculty of Health and Technology,
2Team Danmark, The Elite Sport Organization of Denmark, Brøndby, Denmark
3Human Movement Analysis Laboratory, Department of Orthopaedic Surgery, Copenhagen University Hospital, Amager-Hvidovre, Hvidovre, Denmark
4National Research Centre for the Working Environment, Copenhagen, Denmark
5Sport Sciences, Department of Health Science and Technology, Aalborg University, Denmark
Conflicts of interest
Corresponding author: Mette Kreutzfeldt Zebis E-mail corresponding author: email@example.com