What is the Influence of Visual-motor Reliance on Planned and Unplanned Change of Direction Biomechanics 7 Months Post Anterior Cruciate Ligament Reconstruction?

The majority of anterior cruciate ligament (ACL) injuries occur during non-contact mechanisms.This suggests that an individual's movement technique is a significant factor in the cause of the injury. Hence, ACL injuries are increasingly being framed as an error in motor planning and execution.

Rehab following an ACL reconstruction (ACLR) commonly follows a pathway of: regaining ROM, strength development, power development, running, return to training and then return to competition. However, several studies utilising functional brain MRI and electroencephalogram have demonstrated dysfunction within the somatosensory and visual systems in the ACLR population even after the completion of rehabilitation. This has been suggested to indicate that the ACLR population becomes reliant on their visual system during motor planning and execution, potentially increasing the risk of reinjury.

It has been demonstrated in studies utilising functional brain MRI and EEG that following ACLR, individuals have increased activation of the visual system during simple motor tasks as compared to healthy controls. This is suggested to represent an increased reliance on the visual system during motor planning and execution. Increased reliance on the visual system may negatively affect an individual's ability to respond to sporting situations which are often chaotic in nature, resulting in an inappropriate movement technique being employed. This may then result in an increased risk of reinjury. However, no study to date has been able to assess how visual reliance affects change of direction biomechanics.

The study will recruit individuals who are 7 months post-ACLR and intend on returning to multi-directional field sport. Individuals will complete a stepping down task (eyes open versus eyes closed) to identify participants who are reliant on their visual system. Participants will then complete a 90 deg change of direction task in a planned and then unplanned condition. Those who are visually reliant will be compared to those who are aren't with regards to their unplanned change of direction biomechanics and also the change in their biomechanics from a planned to unplanned condition.

Eligibility Criteria:
Inclusion Criteria:

* Aged 18-35 years old
* Playing club level Gaelic football or hurling
* They must report that they intend on returning to sport at the same or higher level
* Able to give written informed consent and to participate fully in the interventions
* At 7 months biomechanical testing, individuals would need to have 70% symmetry of both quadriceps and hamstring peak torque as measured on our isokinetic dynamometer with the angular velocity set to 60°/s
* Individuals should have already commenced linear running and double leg jumping tasks as part of their rehabilitation
* They are currently attending a gym or can attain gym access for the duration of intervention period

Exclusion Criteria:

* They have not commenced running or jumping in their rehabilitation
* Revision ACL
* They underwent concurrent meniscal repair, chondral repair or extra-articular augmentation
* Serious medical conditions preventing them from completing high intensity resistance exercise
* Any previous: injuries to the visual system, concussion, head injury, unexplained seizures or epilepsy
* Any previous ankle or knee injuries
* Those who are uncomfortable or do not want to hop with their eyes closed (one of the assessment tasks will involve hopping on one leg with their eyes open and followed by another set in which their eyes are closed