Research Interests

Human movement is dependent upon central and peripheral neural strategies that must integrate to activate and coordinate skeletal muscle; with differing mechanical properties and across various situations. The primary goal of research in the Neuromuscular Physiology Laboratory is to provide a better understanding of this neural integration through the study of the motor unit, as it relates to the production and control of force.  For this purpose, we measure both neural signals and motor output eg) strength, force and steadiness.  Our studies concentrate on both normal physiology and its variance across AGE and between SEXes, as well as in altered situations of Parkinson ’s disease, Obesity, and high performance training.  Our funded work has both an applied and basic research ‘arm’.

Jenn's Lab

Primary tools in my lab include: surface and indwelling electromyography (EMG), electrical muscle stimulation, force steadiness in static and dynamic voluntary contractions, as well as ultrasonography to measure muscle and tendon. I have established collaborations to supplement these tool with magnetic cortical stimulation, motion analysis, blood flow and metabolites. As a member of the Institute of Health Living and Chronic Disease Prevention there is research capacity and collaborations where we extend both the lab and community studies to enhance population health.

Applied 'Arm' Research

COMMUNITY-BASED RESEARCH:

Ultimately, what is done in the lab must be relevant to functional movement during real life. My applied research program focuses on:

Quantifying, muscle activity that necessitates functional activities of daily living in older adults.

My work has demonstrated that muscle activity can be measured during the pursuit of real life activities with portable electromyography (EMG) in both young and old adults. My work applies an innovative data analysis technique to quantify low-level muscle activity measured from surface EMG that is recorded OUTSIDE the lab during daily life (~8 hours) with limited constraints to normal movements. These measures of muscle activity are paired with assessment of physical activity and mobility in collaboration with Dr. Jones.

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Basic Research

Example Motor Unit Experiment

Example Motor Unit Experiment

LAB-BASED RESEARCH: The motor unit (MU) is the final element in force production.

My laboratory work has determined an age-related decline in motor unit activity that is sensitive to stress, position and sex. The long-term objective of my research program is to determine the underlying cause of sex differences in functional movement in older adults.

My immediate objective is:

Use isometric force steadiness as a model of functional movement and resolve the contribution of descending and reflex control to modulating motor neuron output in close synergistic muscles.

The observation of 'task-specific' motor unit recruitment and rate coding strategies is studied through alterations in forearm position during elbow flexion. Our recent studies involve following the same motor unit in different forearm positions. We determined that there are sub-populations of motor units that respond independently to forearm movement. This compartmentalized activation contributes to a decline in steadiness with increased age, and reduced steadiness in women compared to men. Through these designs of isometric steadiness and compartmentalized activation of motor units I continue to explore spinal networks of the biceps brachii through combined investigations of reflex feedback and supraspinal input.

Current Projects

My research program centres on understanding how afferent feedback and descending drive alters motor unit output.  Questions are addressed that focus on understanding how alterations in the input and output of spinal motor neurons impact force production and control as we age in men and women.  Studies are conducted in men and women across the lifespan and in disease (Parkinson’s disease, Stroke, obesity) and condition (training, fatigue, frailty) altered states.

Currently the lab is focussing on three objectives which underpin these basic research initiatives:

1. What is the consequence of altered afferent feedback on motor neuron output and force steadiness?  This initiative is underway by measuring fascicle length and tendon properties with ultrasound. Also, tendon vibration and electrical stimulation are being used to alter afferent feedback and determine spinal output. Both measures are applied to understanding force steadiness.
2. Is there a role for task specificity in functional movement? This objective is primarily being studied relative to motor unit output during functional tasks.  To-date there is minimal information on the control of spinal output during real-life functional tasks.
3. Is muscle strength a principal regulator in force steadiness?  A variety of initiatives are underway evaluating how absolute strength impacts force control of isometric and anisometric movements.

Program of Research and students involved have been funded from NSERC, UBC and CFI.