The effects of altering the co-activation ratio of the agonist and antagonist muscle groups on skeletal muscle motor recruitment pattern following ACL surgery and during rehabilitation.

Presenter: Jafed Cortes

Presenter Status: Undergraduate student

Academic Year: 22-23

Semester: Spring

Faculty Mentor: Bulent Sokmen

Department: Kinesiology

Funding Source/Sponsor: RSCAP

Abstract:
During functional movement, both agonist and antagonist muscle groups are equally important in completing an exercise. When an agonist muscle is fatigued, the corresponding antagonist muscle compensates in the joint action and force production; this might pose a concern following anterior cruciate ligament (ACL) injuries that lead into quadriceps atrophy. If the antagonist muscle groups dominate the movement of that joint, it might further extend the rehabilitation process. Therefore, the purpose of this study is to investigate the impact of pre-fatigued antagonist muscle groups on agonist motor unit recruitment patterns in post-ACL-surgery and healthy subjects. 24 healthy males and females (12 post-ACL-surgery) with no orthopedic limitations participated in this study. Following standardized warm-up, subjects’ vastus medialis and biceps femoris muscle activity was monitored via EMG as they performed 1 set of 10 repetitions of modified Peterson step-up in a random order. They performed 30 maximal repetitions of voluntary knee flexion at 60•s-1 on both the affected and non-affected leg (ACL subjects) and dominant and non-dominant leg (healthy subjects) and again 1 set of 10 repetitions of Peterson step-up technique in an identical manner prior to isokinetic knee flexion. The 30 repetitions of isokinetic knee flexion at 60•s-1 resulted in a significant drop in peak torque in all groups (P<0.05). Although there were no significant changes in EMG activity of vastus medialis and biceps femoris from pre- to post- fatiguing isokinetic knee flexion, the vastus medialis to biceps femoris EMG activity ratio was significantly elevated in the affected leg in ACL-injured and non-dominant leg in healthy participants (P<0.05). In a physical therapy setting, manipulating antagonist muscle groups might improve the activity of atrophied muscle.