The Clinical Utility of Torque-Velocity Relationships following Anterior Cruciate Ligament Reconstruction

Following anterior cruciate ligament reconstruction (ACLR), patients are plagued by persistent muscle weakness and increased risk of ACL reinjury. Multidimensional test batteries of patient function are often used to determine which patients are prepared to return to their previous level of activity with minimal reinjury risk. These test batteries often focus primarily on single data points from quadriceps strength testing to determine patient capacity. The torque-velocity relationship posits that as contraction velocity increases, torque production should naturally decrease. Using strength testing data from distinct isokinetic velocities to characterize the torque-velocity relationship, an inherent feature of skeletal muscle, may give clinicians a greater understanding of underlying changes following ACLR. Manuscript I focused on the ability of the torque-velocity relationship to determine which patients would fail to progress upon serial assessment. The primary finding was that the torque-velocity relationship was predictive of satisfactory knee extensor strength and patient self-reported function at a later time point. Manuscript II focused on the ability of the torque-velocity relationship to predict which patients would sustain a subsequent ACL injury. The primary finding was that the torque-velocity relationship was mildly predictive of subsequent ACL injury. Manuscript III focused on how the torque-velocity relationship related to measures of arthrogenic muscle inhibition (AMI). The primary findings were that two-point torque-velocity measurements seemed more closely related to central activation than corticospinal excitability. The torque-velocity relationship may be a novel way to interpret data from commonly employed tests of muscular function. To model distinct demands of muscle, test velocities should be sufficiently different to be additive compared to singular velocity testing. The torque-velocity relationship can give clinicians an understanding of underlying changes in physiology that patients face following ACLR.