Quadriceps weakness develops rapidly after anterior cruciate ligament (ACL) injury and surgery. Despite aggressive rehabilitation, most people have noteworthy quadriceps weakness when they return to activity. This persistent quadriceps weakness has been associated with altered gait patterns, reduced functional performance, and poor long-term knee health-related quality of life. Emerging evidence also indicates that quadriceps weakness plays a crucial role in the development of post-traumatic osteoarthritis ? a negative outcome that is inevitable in almost 50% of this population. Thus, there is a pressing need for new, clinically- feasible intervention strategies to improve quadriceps function after ACL injury and surgery. We hypothesize that a lack of task-specific training elements in current rehabilitation approaches is the underlying reason for the inability to optimally address persistent asymmetry in knee strength and gait after ACL surgery. Accordingly, the current proposal aims to improve quadriceps function in individuals with anterior cruciate ligament (ACL) reconstruction via a novel paradigm, termed as functional resistance training. Progressive functional resistance training will be performed during walking for 8-weeks using a low-cost wearable robotic brace that is capable of providing scalable resistive torques. Various knee-related biomechanical, neuromuscular, and clinical outcomes will be evaluated both before and after the intervention, and will be compared with a dose-matched control group. The effects of progressive functional resistance training during gait on cortical and spinal reflex excitability will also be evaluated to understand the mechanistic underpinnings of improvements mediated by the intervention. The results of the proposed studies will establish the feasibility of functional resistance training to normalize biomechanical and neuromuscular profiles in individuals with ACL reconstruction. More importantly, the proposed application, if successful, may serve as a foundation for a novel paradigm to target quadriceps dysfunction in individuals with a wide range of knee injuries.

Public Health Relevance

Profound quadriceps weakness is ubiquitous after anterior cruciate ligament (ACL) reconstruction, and current rehabilitation approaches are not successful in optimizing quadriceps strength and knee function even years after the surgery. We hypothesize that suboptimal strength and functional outcomes after ACL surgery are due to the lack of task-specific exercise elements during strength training. This application seeks to assess whether progressive functional resistance training during gait will significantly improve quadriceps function, neural excitability, and knee mechanics during gait. The proposed studies will not only lay the foundation for a novel training paradigm, but will also improve our understanding of the mechanisms mediating neuromuscular and biomechanical changes after functional resistance training.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21HD092614-02
Application #
9534715
Study Section
Musculoskeletal Rehabilitation Sciences Study Section (MRS)
Program Officer
Cruz, Theresa
Project Start
2017-09-01
Project End
2019-08-31
Budget Start
2018-09-01
Budget End
2019-08-31
Support Year
2
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Physical Medicine & Rehab
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Krishnan, Chandramouli; Washabaugh, Edward P; Reid, Courtney E et al. (2018) Learning new gait patterns: Age-related differences in skill acquisition and interlimb transfer. Exp Gerontol 111:45-52
Washabaugh, Edward P; Krishnan, Chandramouli (2018) A wearable resistive robot facilitates locomotor adaptations during gait. Restor Neurol Neurosci 36:215-223