Normal EMG

Normal EMG Activity

Volume II - Part I


Objectives
1 - Subjective assesment of MUP waveform and firing rate.
2 - Manual measurements of the MUP and IP.
3 - Correlate EMG waveform with it's sound.
4 - Recognize differences in EMG signals from different normal muscles.

Paraspinal


Normal Insertional Activity
(Note the Frequency of Spikes)

Sharp MUP: 1 mV, 10 Hz
Many Distant MUPs

Abductor Pollicis
Brevis


Complex Waveforms: MUP Superimposition

Full Pattern at Maximal Effort

First Dorsal
Interosseus


Simple MUPs: 500 - 2200 uV,
11 Hz

Full Pattern,
4 mV Envelope Amplitude

Extensor Digitorum
Communis


MUPs Resembling Positive Sharp Waves

Min - Max Effort
2 Trials at 2 sec/div, 1 mV/div

Biceps
Brachii


2 Simple MUPs: 500 - 700 uV,
8 - 10 Hz

Peaks of High/Low Amplitude,
Long/Short Duration

Triceps


2 Simple MUPs: 1000-1500 uV,
Small Distant MUP

Normal Recruitment Frequency: 10 Hz

Full IP at Fast Sweep (10 ms/div)

IP at Slow Sweep:
3 Trials: 2 sec/div, 1 mV/div

Deltoid


Serrated MUPs (?)
Many Distant MUPs

Maximal Effort, 3 Trials
2 sec/div, 1 mV/div
2 - 3 mV Envelope Amplitude

Gluteus
Medius


Several Simple and Complex MUPs

Min to Max Effort
2 Trials: 2 sec/div, 1 mV/div

Vastus
Medialis


Simple MUPs
Normal Recruitment Frequency (10 Hz)

2 Simple MUPs
300 - 900 uV, 8 - 10 Hz

Full IP at Fast Sweep (10 ms/div)

Min to Max Effort
2 Trials: 2 sec/div, 1 mV/div

Tibialis
Anterior


One Sharp MUP: 500 uV, 8 - 9 Hz
Many Distant MUPs

Many Near MUPs: 500 - 1800 uV

Full IP at Fast Sweep

Normal Amplitude on Slow Sweep
Min to Max Effort
2 Trials: 2 sec/div, 1 mV/div

Medial
Gastrocnemius


Simple and Polyphasic MUPs

Full Pattern at Maximal Effort

3 Trials: Min - Max Effort
2 sec/div, 1 mV/div
Note Variation in Amplitude

Orbicularis
Oris


Small Fast Firing MUP
That's Normal

Recruitment of Second MUP

More Recruitment, Polyphasic MUP

Tongue


Many MUPs:
Short, Simple, 200 - 400 uV

Many MUPs at Maximum Effort
Note the Amplitude

EMG at Slow Sweep: Min to Max Effort


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