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ELECTROMYOGRAM

ELECTROMYOGRAM. Amit Sethi Pre-doc Rehab Sciences, MS OTR/L. INTRODUCTION. Electromyogram (EMG) i s a technique for evaluating and recording the activation signal of muscles. EMG is performed by an electromyograph , which records an electromyogram .

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ELECTROMYOGRAM

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  1. ELECTROMYOGRAM Amit Sethi Pre-doc Rehab Sciences, MS OTR/L

  2. INTRODUCTION • Electromyogram (EMG) is a technique for evaluating and recording the activation signal of muscles. • EMG is performed by an electromyograph, which records an electromyogram. • Electromyograph detects the electrical potential generated by muscle cells when these cells contract and relax.

  3. INTRODUCTION Contd. EMG Apparatus Muscle Structure/EMG

  4. ELECTRICAL CHARACTERITICS • The electrical source is the muscle membrane potential of about -70mV. • Measured EMG potentials range between < 50 μV up to 20 to 30 mV, depending on the muscle under observation. • Typical repetition rate of muscle unit firing is about 7-20 Hz. • Damage to motor units can be expected at ranges between 450 and 780 mV

  5. ELECTRODE TYPES Intramuscular - Needle Electrodes Extramuscular - Surface Electrodes

  6. EMG PROCEDURE • Clean the site of application of electrode; • Insert needle/place surface electrodes at muscle belly; • Record muscle activity at rest; • Record muscle activity upon voluntary contraction of the muscle.

  7. EMG Contd. • Muscle Signals are Analog in nature. • EMG signals are also collected over a specific period of time. Analog Signal

  8. Amplification & Filtering Signal pick up Conversion of Analog signals to Digital signals Computer EMG Contd. EMG processing:

  9. APPLICATION OF EMG • EMG can be used for diagnosis of Neurogenic or Myogenic Diseases. • You tube link of EMG

  10. SAMPLE EMG DATA

  11. BIOMECHANICS • Biomechanics is the research and analysis of the mechanics of living organisms. • KINEMATICS – The branch of Biomechanics concerned with describing the motion of bodies. • KINETICS- The branch of biomechanics concerned with explaining the causes of body motions.

  12. KINEMATICS Contd. • Data is usually collected with Motion Capture Devices over a specific time period. • VICON • Motion Analysis Corporation • Qualysis Typical Set up of Motion Analysis Lab

  13. SAMPLE KINEMATIC DATA

  14. SAMPLE KINEMATIC DATA

  15. SAMPLE KINEMATIC DATA

  16. KINEMATICS DATA ANALYSIS • Aim: to identify the variability in reaching movement in normal and stroke individuals. • Outcome Variable: Elbow Joint Angle. • Magnitude of variability was analyzed with Std. Deviation. • Structure of variability in elbow angles was computed via IE using MATLAB. H = Log2 (1/Pi) Pi = probability that a given event will occur. Pi α1/H. • Higher values of IE suggest - more uncertainty. • Lower values of IE suggest- less uncertainty (increased stability). of

  17. RESULTS Subject SD Pre SD Post IE Pre IE Post 1 4.54 1.80 0.58 0.80 2 3.69 2.67 0.79 0.50 Control SD = 2.68 IE = 2.33

  18. CONCLUSION • Variability/Uncertainity in movement is higher in normals as compared to individuals with Stroke. • This variability could be correlated with adaptability in movement which is decreased upon nervous system damage in Stroke. • Large data is required to generalize these results.

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