Biomechanical evaluation of landing maneuvers in soccer players with an anterior cruciate ligament reconstruction

This dissertation is composed of 3 studies. The first study included the following purposes 1) to evaluate within-session reliability of kinematics and kinetics during 2 landing tasks to determine the number of trials needed to achieve acceptable reliability, 2) to determine between-session reliability of kinematics, kinetics, and F-Scan system during the 2 landing maneuvers performed by healthy soccer players, 3) to evaluate the validity (concurrent validity) of the F-Scan system in relation to a platform system as a criterion reference during both landing maneuvers. The results indicated that F-Scan and 3D motion analysis systems are reliable during planned and unplanned landing maneuvers in healthy soccer players. Additionally, both landings can be used as functional tasks to assess lower extremity performance in this population if 4 trials of each landing are used in order to achieve good trial-to-trial reliability. Moreover, the F-Scan system is a valid instrument to measure ground reaction forces during planned and unplanned landing maneuvers.

The second study aimed to compare kinematics, kinetics, and neuromuscular performance between soccer players with an ACLR and healthy non-injured soccer players during planned and unplanned landing maneuvers. The results showed that unplanned landing demonstrated greater injury predisposing factors compared with planned landing by exhibiting a stiff landing technique characterized by decreased hip and knee flexion angles. Generally, soccer players with ACLR showed nearly similar landing mechanics and neuromuscular strategies to healthy non-injured soccer players during both planned and unplanned landing maneuvers. However, soccer players with ACLR appear to utilize a protective landing strategy by decreasing activation of the gastrocnemius muscle, when averaged across both landing tasks.

The purpose of the third study was to evaluate the effect of fatigue on landing biomechanics during an unplanned landing task in soccer players following ACLR compared with healthy non-injured soccer players. The results indicted that fatigue caused changes in landing biomechanics; however, these changes were not significantly different when the groups were compared. These results indicate that having an ACLR (at least 1 year post-surgery) does not appear to lead to sustained changes in landing biomechanics induced by fatigue.