Electromyography

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Electromyography
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What does an EMG signal look like?

• Raw EMG Signal
• Positive and negative
• Result of propagation of signal as passes beneath
  electrode
• Difficult to interpret

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How can we improve interpreting capabilities?

• Full Wave Rectification
• Takes signal and makes it positive
• Linear Envelop Detector
• Take FWR signal and send through a low-pass
  filter at 6-10 Hz
• All produce a signal that follow trends of raw
  signal but with less variability

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Characteristics of the Data

• Amplitude
• Signal Duration
• Timing changes in the signal
• Sequencing of muscle activity across multiple
  muscles

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Quantifying the EMG Signal

• Peak Amplitude
• Integrated EMG (IEMG)
• Average EMG (AEMG)

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Quantifying the EMG Signal

• Peak Amplitude
• Integrated EMG (IEMG)
• Average EMG (AEMG)
• Frequency Analysis

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Comparison Across Different Conditions, People,
etc

• Normalization
• Maximum Voluntary Contraction (MVC)
• Average Value
• Use cyclic movement
• Standard Level of Resistance
• 50 of maximum tension force
• Baseline

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Influences on Signal

• Noise
• Common Mode Rejection
• Depth of muscle
• Conduction velocities
• Levels of recruitment
• Skin
• Fatigue
• Type of Contraction
• Speed of Contraction

• Joint Position
• Electrode Type
• Electrode Placement
• Fixed Wire vs Telemetry
• Psychological Factors

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Applications of EMG

• Physiotry
• Biofeedback
• Strength training and re-education
• Functional Electrical Stimulation
• Balance
• Clinical Gait