The purpose of this study is to examine if the changes in corticospinal function that accompany ACL reconstruction can be improved through a form of mental coaching and encouragement, known as operant conditioning.

It is theorized reduced corticospinal excitability contributes to quadriceps dysfunction after knee injury and joint disease. Current rehabilitation does not directly target the alterations in corticospinal excitability, which may limit recovery. Operant conditioning is an emerging approach capable of increasing corticospinal excitability by directly targeting the corticospinal pathways. However, it remains to be determined whether operant conditioning of the corticospinal pathway may improve corticospinal function after knee trauma. Therefore, this study will evaluate the ability of operant up-conditioning of the corticospinal pathway to improve corticospinal function after ACL reconstruction.

Inclusion Criteria:

• aged 14-45 years
• suffered an acute, complete ACL rupture
• have undergone ACL reconstructive surgery
• willingness to participate in testing and follow-up as outlined in the protocol

Exclusion Criteria:

• have suffered a previous ACL injury on the contralateral leg
• have undergone previous major surgery to the contralateral knee
• have a history of recent significant knee injury (other than ACL) or lower-extremity fracture
• have a history of uncontrolled diabetes or hypertension
• be pregnant or plan to become pregnant
• have metal implants in the head
• have electronic devices in their ear or heart (e.g., cochlear implants or cardiac pacemakers)
• have unexplained recurrent headaches
• have a recent history of seizure
• have a history of repeated fainting spells