Transcript Neuromuscular Aspects (1)

Biomechanics of Skeletal Muscle
and 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 ),
Muscle
structure
The motor
unit
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)
Threecomponent
model of
muscle
contraction
Lengthtension
relationship
ForceVelocity
relationship
Electromyography: The analysis of
muscle electrical activity
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 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 found
DeLuca, C. J. (1997) “The use of surface electromyography in
biomechanics”
on delsys.com website). Click on “library”, then “tutorials”, then article title.