ELECTROMYOGRAM Amit Sethi Pre-doc Rehab Sciences, MS OTR/L.
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Transcript of ELECTROMYOGRAM Amit Sethi Pre-doc Rehab Sciences, MS OTR/L.
ELECTROMYOGRAM
Amit Sethi
Pre-doc Rehab Sciences,
MS OTR/L
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.
INTRODUCTION Contd.
EMG Apparatus Muscle Structure/EMG
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
ELECTRODE TYPES
Intramuscular -
Needle Electrodes
Extramuscular - Surface Electrodes
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.
EMG Contd.EMG Contd.
• Muscle Signals are Analog in nature.
• EMG signals are also collected over a specific period of time.
Analog Signal
EMG Contd.EMG Contd.EMG processing:
Amplification & Filtering
Signal pick up
Conversion of Analog signals to Digital signals
Computer
APPLICATION OF EMG
• EMG can be used for diagnosis of Neurogenic or Myogenic Diseases.
• You tube link of EMG
SAMPLE EMG DATA
BIOMECHANICSBIOMECHANICS
• 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.
KINEMATICS Contd.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
SAMPLE KINEMATIC DATA
SAMPLE KINEMATIC DATA
SAMPLE KINEMATIC DATA
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
RESULTS
Subject SD Pre SD Post IE Pre IE Post1 4.54 1.80 0.58
0.80
2 3.69 2.67 0.79 0.50
Control SD = 2.68 IE = 2.33
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.