2. Muscle function
ā¢ Muscles are the physiological motors of the
human body
ā¢ Kinematics and kinetics give us a good
indication of the muscle groups
ā¢ For increased specificity we measure a muscles
activity during gait
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3. Electromyography
ā¢ Definition of Electromyography (EMG)
ā Electromyography (EMG) is the detection and
recording of the electrical signal produced by
muscle tissue as it contracts.
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4. Muscle activation (sEMG)
ā¢ Measurement of electrical signals within the
muscle with two electrodes
ā¢ A summation of the action potentials generated
during contractions due to a change in the cellās
membrane potential
ā¢ The size of the signal is dependent on the
number and frequency of firing of motor units
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5. Why measure sEMG?
ā¢ Measuring the muscle activity during gait allows:
ā an indication to whether the muscle is active
ā to see relative changes in timing of the muscles
ā to assess motor control and coordination
ā to determine any evidence of spasticity
ā to evaluate muscle function post-surgical transfer
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6. EMG does not tell us:
ā¢ The strength of the muscle
ā¢ What type of movement the signal represents
ā¢ Whether the activity is compensatory or the
primary abnormality.
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7. Electromyography
ā¢ EMG includes the
ā Detection
ā Amplification
ā Recording
ā Processing and analysis
ā Interpretation
ā¢ Three ways of recording the signals
ā¢ Surface electromyography (sEMG) most popular
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8. How to measure sEMG
ā¢ Positioning the patient
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Recommendations: www.seniam.org
9. How to measure sEMG
ā¢ Determine the electrode location
Recommendations: www.seniam.org
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10. How to measure sEMG
ā¢ Skin preparation
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Recommendations: www.seniam.org
11. How to measure sEMG
ā¢ Place and fix the electrodes securely
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Recommendations: www.seniam.org
19. Factors that affect sEMG signal
ā¢ Impedance of the tissue
ā¢ Cross-talk between muscles
ā¢ Changes in geometry between muscle and
electrodes
ā¢ External noise
ā¢ All of these can be reduced using the 3Pās
ā Position, Preparation and Placement of the electrodes
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20. Repeatability and Interpretation
of EMG data
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ā¢ Very few studies in the general literature
ā¢ Displayed the same way as general gait data
ā¢ Normalisation methods need to be appropriate
ā¢ sEMG alongside kinematics and kinetics can
offer further details about muscle function
ā¢ However, many labs choose specific individuals