Biomechanics of Skeletal Muscle and Electroymography Readings: Hamill pp 76-81, 103-109 Electromyography Readings: Hamill pp 81-85; Cram pp 32-37, Ch 3; DeLuca website tutorial (http://www.delsys.com ),

Factors Influencing Production of Muscular Tension and Applied Force Motor unit size Muscle Fiber Type Selective recruitment of fiber types: SO FOG FG Length - tension relationship Force-velocity relationship Angle of pull

Muscle structure

The motor unit

Muscle Fiber Types

Recruitment proceeds from smallest fibers to largest (the size principle)

Three-component model of muscle contraction

Length-tension relationship

Angle of pull affects turning effect, or torque

Length-tension, Angle of Pull Combined

Force- Velocity relationship

Electromyography The electromyogram Recording the Electromyogram Factors affecting electromyogram Analyzing the electromyogram Applications of electromyography

The EMG signal

Recording the electromyogram Electrodes – Size Number Placement Signal conduction – wires or telemetry? Signal conditioning Amplification Filtering Analog to digital conversion Integration Frequency analysis

Filtering: Effect of different cutoff frequencies on EMG

Factors affecting the electromyogram

Analyzing the EMG signal

The concept of Frequency decomposition

Converting EMG from time domain to frequency domain What is the time block, Or window over which Frequency analysis is done?

EMG in the Frequency Domain

Applications of electromyography Timing of excitation Degree of excitation Normalization procedures Muscle force-emg relationship Muscle fatigue Clinical gait analysis Ergonomics Limitations of EMG

Timing and degree of excitation

EMG-force relationship

Electromechanical delay

Windowing is a critical step in converting EMG signal from time to frequency domain

The fatigue index From EMG – Review the Assumptions Inherent in this procedure

Website article reading assignment Go to website: http://www.delsys.com and download tutorial article on surface electromyography detection and recording Be prepared to answer the following questions: What is differential amplification? What is common mode rejection ratio? Where should electrodes be placed? Where should electrodes not be placed? How large should electrodes be? Name 3 applications of EMG signal

Further readings (optional) on Emg methodology DeLuca, C. J. (1997) The use of surface Electromyography in biomechanics. J Appl Biomech, 19:135-163. (can be found on delsys.com website) Morrish, G. (1999) Surface electromyography Methods of analysis, reliability, and main applications Physical and Rehabilitation Medicine, 11:171-205.