Neuromuscular control of joint stability and knee loading during weight bearing

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The longterm goal of my research program is to answer the following questions: (1) is there an optimal muscle activation strategy to optimise functional knee joint stability?; (2) what does the central nervous system (CNS) use as input to govern this strategy?; (3) can individuals with knee instability learn this strategy? The first question is the basis of my NSE research and to answer it I have developed three complimentary research streams: in vivo measurements of electromyography (EMG), kinematics and ground reaction forces (GRF) during controlled static and dynamic tasks; in silico modelling of these tasks which provides relationships between the EMG, kinematics, kinetics and CNS control strategies; in vitro simulation of our in vivo and in silico results to serve as a validation for our hypotheses and test strategies we identify as key to knee stabilisation. With NSERC’s support over the past 5 years we (myself and my trainees) have developed and validated a new in vivo protocol to measure muscle activations during force-controlled weight bearing tasks (3 publications), a new and more robust concatenated non-negative matrix factorisation framework to identify muscle activation synergies (2 submitted papers), a tool to identify muscle inhibition in a musculoskeletal modeling framework and improve the validity of their muscle force outputs (paper in submitted MSc thesis) and a unique in vitro knee joint simulator with 6 degree of freedom tibio-femoral kinematics dictated by the applied musculoskeletal-model-based muscle loads (2 papers in a submitted MSc thesis). To make our analyses as biofidelic as possible, we are currently developing an EMG-augmented musculoskeletal modelling framework to improve our estimates of muscle loads, an endeavour recognised by the NIH National Center for Simulation in Rehabilitation Research at Stanford University with a scholarship for my trainee). This work has also contributed to my trainee success, as all my current graduate students hold funding awards. The objectives of this research program are to (1) explore the link between neuromuscular synergies and joint loading at the knee; (2) establish a clear relationship between directional knee joint stability and the activation of individual muscles crossing the knee joint; (3) identify control strategies used by the central nervous system to optimise stability. Beyond this application, a longterm goal will be to take advantage of training and neural plasticity to evaluate the human capacity to improve stability through optimised training. This information will form the backbone for evidence based diagnostic and intervention strategies focused on individuals who display joint stability deficits. Our research will serve to fill a knowledge gap with respect to neuromuscular control of the lower limb and it can lead to a direct impact on the NSE community and industry.