1. EE 4BD4 Lecture 10
Electromyography

2. Goals of Electromyography
Diagnosis (Identify Neuromuscular Disease, e.g. ALS, muscular dystrophy)
Determine extent of disease and monitor progress
Study control of muscles during movement
Measure dysfunction and propose solutions
Study normal anatomy and physiology

3. Surface Diagnostic Techniques (Motor and Sensory Conduction)

4. Patient Instrumentation (Sensory and Motor Conduction Velocity)

5. Stimulation at Wrist

6. Stimulation at the Elbow

7. Pathological Findings
Some Loss
of Axons
Demyelinating
Condition
Complete Loss

8. Motor Unit Electrical and Mechanical Responses

9. Invasive Techniques Measure motor unit action potentials (MUAPs)
Recorded from voluntary contractions
Information is in shape, duration and amplitude of MUAPs
Considered “gold standard” by physicians
Pattern recognition is subjective except for fibrillation and fasiculation potentials
MUAPs from low threshold units only

10. Selectivity of Recording

11. Needle Recorded EMG

12. Extracting Motor Unit Action Potentials from Higher Level Recordings
Needle Recorded
Signal – Interference
Pattern (20 Hz – 5 KHz)
High Pass Filtered
400 Hz – 5 KHz
Extracted MUAPs by
“Spike Triggered
Averaging”

13. Central Nervous System Identification
Diagnose and monitor diseases of the central nervous system (Parkinsonism)
Assess dysfunction following trauma
Assess effects of intervention (drugs, physiotherapy, surgery)
Study normal muscle control
Prosthesis Control

14. Modeling the Electromyographic Signal

15. Measuring Control of Individual Motor Units Recorded with Single Fibre 25 micron Needle

16. Compressed Single Fibre MUAPs (one to several contributing fibres)

17. Motor Unit Firing Rates

18. Surface Recorded EMG

22. RAW EMG DURING GAIT
LEFT HEMIPLGIC GAIT NO AIDS WALKING SPEED .87 m/sec
LEFT FOOT
RIGHT QUAD
RIGHT HAM
RIGHT TIB ANT
Right GAST.
RIGHT FOOT
50 μvolt Div
TIME SEC

23. EMG PROCESSING Full –Wave Rectification plus LPF EFFECTS OF INCREASING SMOOTHING
LEFT
FOOT
LEFT TIB ANT FULL WAVE RECTIFIED
10 HZ
5 HZ
2 HZ
50 μvolt Div
TIME sec

24. EMG Profiles for Light Hemiplegia Mean Profile plus 1 Std Dev0%
100%

25. EMG Profiles for Severe Hemiplegia Mean Profile plus 1 Std Dev

26. EMG Profiles for Severe Hemiplegia Mean Profile plus 1 Std Dev