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, Canada 1Biomechanics 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

Biomechanics Laboratory, University of Ottawa3 Isometric EMG exponential over full range especially when normalized to maximum force

Biomechanics Laboratory, University of Ottawa4 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

Biomechanics Laboratory, University of Ottawa5 Force-velocity-length force varies with both length and velocity of contraction also pre- history, i.e., prestreched, fatigued, or relaxed

Biomechanics Laboratory, University of Ottawa6 Maximum EMG experiment by Komi measured EMG of three muscles measured maximum force at different speeds of contraction

Biomechanics Laboratory, University of Ottawa7 Maximum EMG results of force similar to Hill’s equation and Gordon & Huxley

Biomechanics Laboratory, University of Ottawa8 Maximum EMG EMGs did not vary across velocity of contraction

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 Ottawa9

Biceps Triceps Angle Velocity Accel. Biomechanics Laboratory, University of Ottawa10 Flexion Extension FlexingExtendingConcentric flexion Concentric extension Concentric flexion by biceps Concentric extension by triceps

Biceps Triceps Angle Velocity Accel. Biomechanics Laboratory, University of Ottawa11 Flexion Extension Low EMG to stop extension Stopping flexion with triceps Stopping extension with biceps

Biceps Triceps Angle Velocity Accel. Biomechanics Laboratory, University of Ottawa12 Flexing Extending Flexion Extension In this trial flexion was stopped by ligaments and bones