electromyography: relationships & applications d. gordon e. robertson, phd, fcsb biomechanics...
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Electromyography: Relationships & Applications
Electromyography: Relationships & Applications
D. Gordon E. Robertson, PhD, FCSB
Biomechanics Laboratory,
School of Human Kinetics,
University of Ottawa, Ottawa, Canada
D. Gordon E. Robertson, PhD, FCSB
Biomechanics Laboratory,
School of Human Kinetics,
University of Ottawa, Ottawa, Canada1Biomechanics Laboratory, University of Ottawa
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Biomechanics Laboratory, University of Ottawa 2
Isometric EMG
• linear relationship for submaximal contractions
• exponential relationship over full range
• can be used as a control signal to regulate myoelectrically controlled devices
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Biomechanics Laboratory, University of Ottawa 3
Isometric EMG
• exponential over full range especially when normalized to maximum force
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Biomechanics Laboratory, University of Ottawa 4
Force-velocity
• Hill’s equation illustrates that as speed of muscle shortening increases, force decreases
• but for eccentric contractions force increases with speed of lengthening
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Biomechanics Laboratory, University of Ottawa 5
Force-velocity-length
• force varies with both length and velocity of contraction
• also pre-history, i.e., prestreched, fatigued, or relaxed
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Biomechanics Laboratory, University of Ottawa 6
Maximum EMG
• experiment by Komi
• measured EMG of three muscles
• measured maximum force at different speeds of contraction
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Biomechanics Laboratory, University of Ottawa 7
Maximum EMG
• results of force similar to Hill’s equation and Gordon & Huxley
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Biomechanics Laboratory, University of Ottawa 8
Maximum EMG
• EMGs did not vary across velocity of contraction
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EMG during Dynamic Contractions
• strong correlation between level of concentric contraction and EMG
• weak correlation between level of eccentric contraction and EMG
• EMG level is often greater during a brief rapid MVC then during a sustained MVC
• following figures show biceps and triceps brachii during a horizontal rapid flexion extension movement, an electrogoniometer was used to monitor elbow angle
Biomechanics Laboratory, University of Ottawa 9
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Biceps
Triceps
Angle
Velocity
Accel.
Biomechanics Laboratory, University of Ottawa 10
Flexion Extension
FlexingExtending
Concentric flexionConcentric extension
Concentric flexion by biceps
Concentric extension
by triceps
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Biceps
Triceps
Angle
Velocity
Accel.
Biomechanics Laboratory, University of Ottawa 11
Flexion Extension
Low EMG to stop extension
Stopping flexion with triceps
Stopping extension
with biceps
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Biceps
Triceps
Angle
Velocity
Accel.
Biomechanics Laboratory, University of Ottawa 12
Flexing
Extending
Flexion Extension
In this trial flexion was stopped by
ligaments and bones