EMG

  1. What is an EMG signal?
    the summation of the various (nerve and muscle) compound action potentials generated during a contraction
  2. What are the surface characteristics of an EMG signal?
    • Frequency range: 10 hz to 10 khz
    • Amplitude: 10 uV to 30 mV (surface)
  3. Why is the EMG signal of each muscle unique?
    Because muscles consist of relatively unique fiber compositions, the EMG signal of each muscle is also unique
  4. What factors affect EMG recording?
    • 1. Location
    • 2. Activity
    • 3. Intrinsic Factors
    • 4. Other factors
  5. What are the components of activity when it comes to EMG recording?
    • Isometric - constant position (think metre, distance, position)
    • Isotonic - constant force
    • Isokinetic - constant speed
  6. Is force to EMG a linear relationship?
    No, except for isometric
  7. What intrinsic factors affect EMG recording?
    • number of fibers active
    • ph
    • blood flow
    • fiber diameter
    • location of active fibers
    • tissue composition
  8. What are some other factors?
    • Cross talk
    • Band pass and spatial filtering
    • AP superposition
  9. What is envelope calculation?
    • Absolute value of raw EMG signal (Rectification) is summated (integrated) over a period of time
    • It can be used in maximal voluntary contraction calculations
  10. What is signal averaging?
    Signals are averaged over a set number of cycles to reduce noise and highlight signal of interest
  11. What are the therapeutic uses of EMG?
    biofeedback


     Used as a tool for re-education of a muscle that demonstrates either

    ­Limited volitional strength

    ­Excessive activity that the individual is not able to volitionally control
  12. What are the diagnostic uses?
    Needle (or fine wire) EMG

    • Muscular component of neuromuscular junction (will also reveal information regarding status of motor nerve supplying muscle)
    • Phasic properties of muscle during functional activity (Kinesiologic)



    Surface EMG

    • Neural component of the motor unit (motor nerve conduction studies)
    • Phasic properties of muscle during functional activity (Kinesiologic)
  13. What is biofeedback?
    The use of electronic instrumentation to provide feedback regarding physiological function for the purpose of increasing one’s awareness of the response and modify that response to a desired level
  14. What are the types of biofeedback?
    úEMG *

    úBlood pressure

    úVisceral/vasomotor responses

    úElectroencephalograph (EEG)

    úHeart rate
  15. Name the characteristics of biofeedback?
    No electrical stimulation is applied to the patient – instead electrical signals from physiological activity is recorded

    • Functions as an intrinsic feedback mechanism
    • Opposed to extrinsic (vision, proprioception, somatosensory)
    • No direct information is contained in EMG regarding force/torque
  16. What are the advantages of biofeedback?
    • speed of feedback response
    • continuity
    • sensitivity
    • objectivity
  17. Electrode placement
    LOOK THIS over - slide 25
  18. What is the electrode placement for a weak muscle?
    úPlace wider apart to increase attenuation

    úAs control is gained move closer together
  19. What is the electrode placement for hypertonicity/spasticity?
    úPlace closer initially to work on one specific muscle or area of muscle

    úAs control is gained move farther apart
  20. How to inhibit/reduce spasticity?
    úTypically work to gain control of relaxation and then focus on recruitment
  21. How do you diminish splinting or guarding due to pain?
    Patient must initially develop awareness of activity, then work to achieve control over relaxation



    úExample : Low Back Pain

     Supine positioning – relaxation of ES

     Sitting position – maintain low level

     Sit-stand and then lifting activites

    úElectrode placement – start with close placement
  22. What is kinesiological EMG?
    The evaluation of muscle activity in relation to the movement of the body segments
  23. Describe concentric and eccentric activity. Note that the context here is that a "kinesiological EMG" is a mix of both of these activities.
    Mix of concentric & eccentric activity

    úConcentric activity occurs in brief bursts – Power generation

     Starts the limb’s momentum going forward and then it turns off to save energy

    úEccentric muscle activity is very energy efficient – Power absorption

     What type (fast twitch or slow twitch) of muscle would you expect to be contracting eccentrically?

    * Note: In understanding muscle in regard to movement, activity will always lead the joint being moved
Author
Anonymous
ID
330739
Card Set
EMG
Description
Clinical Electro
Updated