Theses and Dissertations Collection

The purpose of this study was to (a) assess the symmetry of muscle activation onset, duration, and time to peak muscle activation during a jump-landing task in the left and right vastus lateralis, vastus medialis, biceps femoris, semitendinosus, and to (b) determine how a 6-week plyometric training intervention may impact the symmetry of muscle activation. Previous research has demonstrated that females are at an increased risk for anterior cruciate ligament (ACL) injury. Both modifiable and non-modifiable risk factors have been proposed, including that of neuromuscular control. Past research has demonstrated that coactivation of the quadriceps and hamstrings is suggested to be a favorable movement strategy, thereby, reducing the risk of ACL injury. Electromyography was used to record onset, duration, and time to peak muscle activation of the right and left limbs during a jump-landing task, prior to and following a 6-week plyometric training intervention. Repeated-measures ANOVAs were used to identify if significant differences in activation characteristics were present prior to and following training, as well as between right and left limbs. Results from the present study revealed increased quadriceps activity without equivalent increases in hamstring activity following plyometric training, thus, less favorable coactivation recruitment patterns. These findings prompt inquiry into the value and merit of prescribing plyometric training programs for post-pubescent adolescent females.

Key words: ACL, neuromuscular control, coactivation