BACKGROUND: Diminished corticospinal excitability is theorized to contribute to poor quadriceps function after anterior cruciate ligament (ACL) reconstruction. Operant conditioning of the motor evoked torque (MEP HYPOTHESIS: After ACL reconstruction, patients would demonstrate increases in quadriceps strength, voluntary activation, and corticospinal excitability after a 2-week operant conditioning intervention. STUDY DESIGN: Randomized controlled clinical trial. LEVEL OF EVIDENCE: Level 1. METHODS: A total of 22 patients with reconstructed ACL were randomized into 1 of 2 groups: group 1 received 2 weeks of operant conditioning training on the reconstructed leg to improve their transcranial magnetic stimulation (TMS)-elicited MEP RESULTS: The COND group demonstrated a significantly higher within-session percent increase in MEP CONCLUSION: Operant conditioning training can elicit improvements in corticospinal excitability after ACL reconstruction
however, improvements in quadriceps strength and voluntary activation seem not to be attributed solely to operant upconditioning training. CLINICAL RELEVANCE: Operant conditioning is a promising approach to improve corticospinal excitability after ACL reconstruction. However, optimizing the delivery of operant conditioning protocols by potentially increasing the dosage of operant conditioning and intervening earlier after surgery may be needed to translate these changes to improvements in quadriceps function.