Biomechanics of Skeletal Muscle and Electroymography

Biomechanics of Skeletal Muscleand Electroymography

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 (http://www.delsys.com ),

Musclestructure

The motorunit

Factors Influencing Production of Muscular Tension

Motor unit size Muscle Fiber Type

- Selective recruitment of fiber types:• SO FOG FG

Length - tension relationship Force-velocity relationship

Muscle Fiber Types

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

Three-component

model of muscle

contraction

Length-tension

relationship

Force-Velocity

relationship

Electromyography: The analysis of muscle electrical activity

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

The EMGsignal

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 isdone?

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 ofexcitation

EMG-forcerelationship

Electromechanical delay

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

The fatigue indexFrom EMG –Review the AssumptionsInherent in thisprocedure

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 on Electromyography

•Journal articles with specific review assignments:•Hildenbrand & Noble. (2004) J Ath Trng. Abdominal muscle activity using different exercise equipment. •Caterisano, et al (2002) J Str & Cond Res. EMG of Hip and thigh muscles during back squat.•Anders (2006) ACE FitnessMatters. EMG of gluteus maximus during various hip extension exercises.

•Additional detailed tutorial on methodology (optional):

•Electromyography in biomechanics. J Appl Biomech, 19:135-163. (can be foundDeLuca, C. J. (1997) “The use of surface electromyography in biomechanics” on delsys.com website). Click on “library”, then “tutorials”, then article title.