Functional Resistance Training during Gait: A Novel Intervention to Improve Knee Function after ACL Reconstruction
Investigators: Chandramouli Krishnan, Catherine A. Spino, Mark D. Peterson, Riann Palmieri-Smith, Edward M. Wojtys
Funding: Eunice Kennedy Shriver National Institute of Child Health and Human Development, 2017-2019 (1 R21 HD 092614 01)
Profound quadriceps weakness and activation failure (i.e., the inability to completely activate the quadriceps muscle due to neural inhibition) usually develop rapidly after anterior cruciate ligament (ACL) injury and surgery. Despite the significant progress made in ACL surgery and post-operative rehabilitation over the last few decades, most people have noteworthy quadriceps weakness and activation failure when they return to activity. Data from our own laboratories and others show that quadriceps strength gradually improves over time, but rarely recovers completely even several years after the surgery. This chronic quadriceps weakness significantly alters gait mechanics and contributes to knee instability, disability, and increased knee re-injury rate. Although short-term patient-reported outcomes are very good after ACL reconstruction, an alarming number (up to 50%) of the people sustaining this injury have clear evidence of post-traumatic osteoarthritis within 15 years of injury. Altered movement patterns and abnormal joint loading due to poor quadriceps strength are theorized as the underlying cause of early post-traumatic knee osteoarthritis. Indeed, prospective studies indicate that quadriceps weakness is directly associated with the onset of post-traumatic osteoarthritis after ACL injury and reconstruction. Thus, interventions addressing quadriceps weakness are critically needed to correct abnormal knee biomechanics, minimize or delay the onset of osteoarthritis, and improve knee-health related quality of life outcomes.
The objective of this application is to perform a pilot clinical trial that assesses whether progressive functional resistance training during gait will significantly improve quadriceps function, neural excitability, and knee mechanics during gait. We anticipate that this approach will lead to symmetrical quadriceps strength and gait biomechanics, complete voluntary activation, and improved neural excitability and patient-based outcomes.
Aim 1: Determine the effects of progressive functional resistance training during walking on knee outcomes.
Hypothesis 1: Progressive functional resistance training while walking will result in greater improvements in knee extensor strength & voluntary activation than dose-matched treadmill walking.
Hypothesis 1B: Sagittal plane knee biomechanics, EMG activation patterns during gait, and patient-reported outcomes will also be significantly better after progressive functional resistance training than after dose-matched treadmill training.
Aim 2: Determine the effects of progressive functional resistance training during gait on cortical and spinal reflex excitability of individuals with ACL reconstruction.
Hypothesis 2A: Progressive functional resistance training while walking will result in greater changes in corticospinal excitability than dose-matched treadmill walking.
Hypothesis 2B: There will be a strong association between changes in knee extensor strength, voluntary activation and corticospinal plasticity.