This document provides an overview of electromyography (EMG) including: - EMG measures the electrical activity of active muscle fibers using electrodes placed close to muscles. Rectified EMG signals indicate muscle activity. - Applications of EMG include assessing muscle function, neuromuscular diseases, and prosthetics. - Factors that impact EMG signal quality include signal-to-noise ratio, filtering, and minimizing noise contamination and signal distortion. - Different types of EMG electrodes exist including fine-wire, needle, and surface electrodes, each with their own advantages and disadvantages for measuring muscle activity.

1. Electromyography (EMG)
Presented by
S.Gokila AP/ECE
KIT-Kalaignarkarunanidhi Institute of Technology

2. Introduction
 Measures the electric activity of active muscle fibers.
 Electrodes are always connected very close to the muscle
group being measured.
 Rectified and integrated EMG signal gives rough indication
of the muscle activity.
 Needle electrodes can be used to measure individual muscle fibers.
 Main sources of errors are 50/60 Hz and RF interference.

3. Applications
 muscle function,
 neuromuscular disease,
 prosthesis.

4. Maximizing Quality of EMG Signal
 Signal-to-noise ratio
 Highest amount of information from EMG signal as possible
 Minimum amount of noise contamination
 As minimal distortion of EMG signal as possible
 No unnecessary filtering
 No distortion of signal peaks
 No notch filters recommended
 Ex: 60 Hz

5. Types of EMG
 Electrode Categories
Inserted
Fine-wire (Intra-muscular)
Needle
Surface

6. Fine-wire Electrodes
 Advantages
 Extremely sensitive
 Record single muscle activity
 Access to deep musculature
 Little cross-talk concern
 Disadvantages
 Extremely sensitive
 Requires medical personnel, certification
 Repositioning nearly impossible
 Detection area may not be representative of entire muscle

7. Surface Electrodes
 Advantages
 Quick, easy to apply
 No medical supervision, required certification
 Minimal discomfort
 Disadvantages
 Generally used only for superficial muscles
 Cross-talk concerns
 No standard electrode placement
 May affect movement patterns of subject
 Limitations with recording dynamic muscle activity

8. Characteristics of EMG Signal
 Amplitude range: 0–10 mV (+5 to -5) prior to amplification
 Useable energy: Range of 0 - 500 Hz
 Dominant energy: 50 – 150 Hz

9. Solutions for Signal Interruption Related
to Electrode and Amplifier Design
 Differential amplification
 Reduces electromagnetic radiation noise
 Dual electrodes
 Electrode stability
 Time for chemical reaction to stabilize
 Important factors: electrode movement, perspiration,
humidity changes
 Improved quality of electrodes
 Less need for skin abrasion, hair removal

10. Differential Amplification
 Ambient (electromagnetic) noise is constant
 System subtracts two signals
 Resultant difference is amplified
 Double differential technique

11. Electrode Placement
 Away from tendon
 Fewer, thinner muscle fibers
 Closer to other muscle origins, insertions
 More susceptible to cross-talk
 Away from outer edge of muscle
 Closer to other musculature
 Orientation parallel to muscle fibers
 More accurate conduction velocity
 Increased probability of detecting same signal

12. EMG Electrode Placement

13. Surface Electrode Placement

14. Thank you