Biomechanics of Skeletal Muscle and Electrymography n Biomechanics

Biomechanics of Skeletal Muscle and Electrymography n Biomechanics of skeletal muscle - Readings: Hamill pp 76 -81, 103 -109 n Electromyography - Readings: Hamill pp 81 -85; Cram pp 32 -37, Ch 3; De. Luca website tutorial (see slide 31), Hildenbrand Noble study

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

Muscle Fiber Types

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

Length-tension, Angle of Pull Combined

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

The signal

Recording the electromyogram n Electrodes – - Size - Number - Placement n n 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 of excitation

Applications of electromyography n n Timing of excitation Degree of excitation - Normalization procedures n n n 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 n Be prepared to answer the following questions: n - 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 De. Luca, 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.