Biomechanics of Skeletal Muscleand Electrymography

Biomechanics of skeletal muscle- Readings: Hamill pp 76-81, 103-109

Electromyography- Readings: Hamill pp 81-85; Cram pp 32-37, Ch 3;

DeLuca website tutorial (see slide 31), Hildenbrand and Noble study

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 Fiber Types

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

Length-tension, Angle of Pull Combined

Electromyography

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

The signal

Recording the electromyogram Electrodes –

- Size- Number- Placement

Signal conduction – wires or telemetry? Signal conditioning

- Amplification- Filtering- Analog to digital conversion- Integration- Frequency analysis

Factors affecting the electromyogram

Analyzing the EMG signal

Timing and degree ofexcitation

Applications of electromyography

Timing of excitation Degree of excitation

- Normalization procedures

Muscle force-emg relationship Muscle fatigue Clinical gait analysis Ergonomics Limitations of EMG

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 electromyographyMethods of analysis, reliability, and main applicationsPhysical and Rehabilitation Medicine, 11:171-205.