Needle EMG · Core

Compare neurogenic and myopathic patterns

MUAP morphology & recruitment

Relate motor-unit morphology and number to the force being produced.

3 learning sectionsCompiled 2026-09-08English edition · Traditional Chinese available

01Neurogenic clues

  • Chronic reinnervation may produce longer, larger MUAPs with reduced recruitment.
  • After unit loss, remaining units must fire faster to increase force.

02Myopathic clues

  • Loss of muscle fibers within a unit may create shorter, smaller MUAPs and early recruitment at low force.
  • Severe or chronic myopathy may have mixed morphology; size alone cannot classify it.

03Activation versus recruitment

  • Poor activation may produce slow or incomplete firing. Consider pain, cooperation and central causes.
  • Document effort and compare multiple muscles.

Pause and explain

Explain in your own words: “Recruitment describes the relationship between force, unit number and firing rate.” Then think of a situation in which it could be misinterpreted.

Show a review prompt

Nascent reinnervating units can also be short, small and polyphasic.

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References and further reading

Educational synthesis; independent neuromuscular specialist review is pending. Publication dates and compilation dates are distinct. This is an original teaching synthesis; consult the source for complete methods and criteria.