NCS-EMG (MOTOR UNIT ACTION POTENTIAL, MUAP)

SUMMARY

1. Motor unit action potential (MUAP): compound action potential from muscle fibers belonging to a single motor unit, within the recording range of the needle electrode.

PARAMETERS RECORDED
2. Amplitude: represents the muscle fibers recorded near the needle electrode, affected by the proximity of the needle to depolarizing muscle fibers.
3. Rise time: represents the time it takes the MUAP to go from its baseline to the peak of the negative wave.
4. Duration: represents the number of muscle fibers within the motor unit. Amplitude & duration are proportional to the innervation ratio of the motor unit.
5. Turns & phases.



Figure: motor unit action potential

Reference(s)

Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].