Grant: Discovery Grants Program - Individual

This NSERC supported research program has focused on understanding key factors and their interrelationships that affect the generation and control of skeletal muscle force in humans. By using an integrative systems level approach the primary long term objective is to explore the system at the motor unit level to provide an improved understanding of how the neural output from the spinal cord is translated by skeletal muscle properties into appropriate activation and force control that underlies purposeful movement. The motor unit is the critical functional level of control for these outcomes. Findings from this line of research are applicable to both fundamental systems physiology and applied physiology. The human model offers unique opportunities for advancing knowledge in this area. Importantly, participants can comply with various requisite tasks that reflect normal activities and voluntarily controlled muscle actions in vivo. Experiments involve studying acute (fatigue, potentiation) and chronic adapted states (natural adult aging, training) as models using a combination of innovative techniques and methodologies. Short-term plans and objectives will focus broadly on motor unit properties (recruitment and rate coding and other intrinsic neuronal properties) during dynamic (shortening/lengthening) contractions; in contrast with most all current understanding which has been gained from isometric (static length) contractions.  Furthermore, our recent success with recording motor unit properties in dynamic contractions that are more reflective of human movement will be exploited and expanded under various acute and chronic states of the neuromuscular system (potentiation vs fatigue; effect of muscle length and architecture) and increased activity over hours and weeks (exercise - voluntary and electrically stimulated), and decades (natural aging). Questions include: What are the responses of the neuronal properties when the state of the muscle is changed locally (electrical stimulation or through the normal neuromuscular voluntary pathway? Do neuronal properties adapt when muscle properties (size, architecture, contractility, endurance etc.) are altered (muscle is very adaptable to acute and chronic activation and stress)? And what are the key factors or pathways that might affect these adaptations? These will be outlined as specific rationale and aims with experimental details. Notable in the research program is the unique combination of several techniques either within our laboratory or through established collaborations which allow these questions to be addressed comprehensively with current technologies. These include all aspects of motor unit electrophysiology; peripheral (electrical) activation of the neuromuscular system; spinal and supraspinal factors with TMS; measures of voluntary force or torque (isometric and dynamic); ultrasound and magnetic resonance imaging of muscle.