Two most common methods of EMG analysis
Maximum voluntary contraction (MVC) and Peak dynamic method
Stages of EMG analysis
Preparation, processing, interpretation
Stage 1 of analysis
Raw EMG rectifies to quantify signal amplitude
Why should you rectify the data
Easier to read, standardise amplitude parameters like mean and peak
Stage 2 of analysis
Decide upon processing method
What is average rectified EMG (AREMG)
Average value of the rectified EMG over a given time period
What is integrated EMG
Area under rectified EMG curve (mV/s)
What is Root mean square EMG (RMS EMG)
The square root of the average power (V^2) of the signal over a given time, the most common processing technique
Stage 3 of analysis
Interpret data
Alternative method of processing
Frequency domain analysis
Muscle fatigue
Changes muscle fibre membrane permeability, interferes with the normal propagation of action potentials
Intrinsic factors affecting EMG
- Number of active motor units
- Muscle fibre consumption
- Blood flow in muscle
- Fibre diameter, muscle length
- Depth and location of active fibres
- Adipose tissue
Extrinsic factors affecting EMG
- Electrode configuration
- Electrode location
- Electrode orientation
