Jan - 31 EMG Flashcards
What is electromyography
a technique to measure the electrical activity produced by the of skeletal muscles
you are measuring the summarized activiy in the muscle unit.
does EMG work for smooth muscles?
emg is designed to detect the sudden changes in activity, smooth msucles do not contract voluntarily or durastically, and the emg cannot pick up on the non-durastic change.
what does the EMG measure?
Motor Unit Action Potential (MUAP)
- the action potential in the motor units.
- measure the motor unit level activity.
What are the 2 main types of EMG?
Surface and intramuscular
What is a surface EMG
- Uses electrodes on skin
- non-invasive
- measures the summation of lectrical activity form multiple muscle fibres.
What is the intramuscular (needle EMG)
- the electrodes are attached to a needle and injected into the muscle.
- need a medical professional.
- requires a very good knowledge of the location of the muscles.
what does rectification mean?
- when you have values below zero
- Change the negatives to positive (everything is converted to the absolute values)
why do we need to rectify the raw EMG signlal
- The negative direction does not mean the muscle was less active.
- The signals are bipolar, contain both positive and negative fluctuations
- Helps in creating a more stable representation of msucle activation
- ensures all values contribute meaningfully to signal
why smooth your signal in an EMG
- removes the high frequency noise
- reduces reapid fluctuations by motor unit firing variations
- Reveals trends in muscle activation
- provides a clearer representation of msucle activity over time
- facilitates comparision across trials and subjects
- helps standardize msucle activity data for better analysis.
What is the system for EMG data collection
Delsys EMG System
