EMG Biofeedback


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EMG Biofeedback, physiotherapy

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EMG Biofeedback

  1. 1. Sreeraj S R EMG BIOFEEDBACK
  2. 2. Sreeraj S R Feedback • Feedback is a response to a particular process or activity • According to Weiner, 1948, ‘feedback is a method of controlling a system by reinserting into it the results of its past performance’ • Physiological feedback is a self-regulatory biological system in which the output or response affects the input either positively or negatively
  3. 3. Sreeraj S R Positive Feedback • Change in one direction causes further change in the same direction Uterine contraction Pressure on cervix Oxytocin release
  4. 4. Sreeraj S R Negative Feedback • Change in one direction causes further change in the opposite direction Body Temperature Rises Body Sweats more Body Temperature drops
  5. 5. Sreeraj S R Feedback • Feedback includes information related to the sensations associated with some action as well as information related to the result of the action relative to some goal or objective. • Physiological feedback refers to intrinsic information inherent to movement including kinesthetic, visual, cutaneous, vestibular, and auditory signals collectively termed as response produced feedback
  6. 6. Sreeraj S R Feedback • Feedback from some measuring instrument which provides information about a biologic function is referred to as biofeedback • Also refers to extrinsic information or some knowledge of results presented verbally, mechanically, or electronically to indicate the outcome of some movement performance
  7. 7. Sreeraj S R Definition of Biofeedback • Three professional biofeedback organizations, the Association for Applied Psychophysiology and Biofeedback (AAPB), Biofeedback Certification International Alliance (BCIA), and the International Society for Neurofeedback and Research (ISNR), arrived at a consensus definition of biofeedback in 2008: • “is a process that enables an individual to learn how to change physiological activity for the purposes of improving health and performance. Precise instruments measure physiological activity such as brainwaves, heart function, breathing, muscle activity, and skin temperature. These instruments rapidly and accurately 'feed back' information to the user. The presentation of this information — often in conjunction with changes in thinking, emotions, and behavior — supports desired physiological changes. Over time, these changes can endure without continued use of an instrument. http://en.wikipedia.org/wiki/Biofeedback
  8. 8. Sreeraj S R In Biofeedback 1. The information is detected, 2. provided in an understandable way to the patient who can then, at their own initiation, 3. use the information to achieve a measure of control over the same process. i.e. engaging the patient in a ”closed loop” learning, using feedback until sufficient development of his motor skills occurs, so that an “open loop“ movements can be achieved.
  9. 9. Sreeraj S R Physiologic signal Response by patient Physiologic signal Response by patient Detection and feedback Open Loop Closed Loop
  10. 10. Sreeraj S R every day forms of biofeedback
  11. 11. Sreeraj S R you have to have accurate feedback, of course
  12. 12. Sreeraj S R Requirements • To be realistic and successful, three main elements are needed in order to enhance motor learning: 1.Relevant 2.Accurate 3.Speed of information Most EMG biofeedback devices nowadays introduce 50 to 100 m sec - delays before the signal can reach the ears or eyes of the patient
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  14. 14. Sreeraj S R EMG Biofeedback • Nerve fiber conducts an impulse to the neuromuscular junction • acetylcholine binds to receptor sites on the sarcolemma • inducing a depolarization of the muscle fiber • creates movement of ions and thus an electrochemical gradient around the muscle fiber • Changes in potential difference or voltage associated with depolarization can be detected by an electrode placed in close proximity
  15. 15. Sreeraj S R EMG Biofeedback • EMG does not measure muscle contraction directly • EMG measures electrical activity associated with muscle contraction • Electrical activity of muscle measured in micro volts (1 volt = 1,000,000 V)
  16. 16. Sreeraj S R EMG Biofeedback
  17. 17. Sreeraj S R EMG Biofeedback Advantages: • Can be integrated with other therapeutic interventions • an enhancer of the therapy • reduce patient’s reliance on the therapist • gain control without reliance on the therapist, and once gained, • to maintain control without either the therapist or the machine.
  18. 18. Sreeraj S R Working A biofeedback loop. Here the forearm muscles are monitored to provide a visual readout to the user. The feedback loop is completed when the user alters her muscle tension to adjust the readout.
  19. 19. Sreeraj S R Working 2 active electrodes and 1 reference electrode
  20. 20. Sreeraj S R Working - CMRR • Two signals are fed to a differential amplifier which subtracts the signal from one active electrode from the other active electrode • Differential amplifier uses reference electrode to compare the signals of the two active electrodes • This in effect cancels out or rejects any components that the two signals coming from the active electrodes have in common thus amplifying the difference between the signals • Ability of the differential amplifier to eliminate the common noise between active electrodes is called the common mode rejection ratio (CMRR)
  21. 21. Sreeraj S R Working - filtering • EMG signals are in the range of 0 – 500 Hz • Frequencies above 500 Hz is filtered out • The dominant energy of the EMG signal is in the range of 50 – 150 Hz • Motion artifacts in the range of 0 – 20 Hz • Frequencies below 20 Hz are filtered by using a high pass filter
  22. 22. Sreeraj S R Working – Rectification & Integration Raw EMG activity in muscle is an alternating voltage - direction or polarity is constantly reversing Rectification is the summation of electrical activity. To determine the overall increase and decrease in electrical activity, deflection toward the negative pole must be flipped upward toward the positive pole EMG signal is then smoothed to eliminate the peaks and valleys or high frequency fluctuations The signal may then be integrated by measuring the area under the curve for a specified period of time. Integration forms the basis for quantification of EMG activity.
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  24. 24. Sreeraj S R Visual cues 1. Meter read outs 2. Flashing lights 3. Oscilloscope 4. Computer screens Auditory cues 1. Changing tones 2. Clicks
  25. 25. Sreeraj S R Features of the BF Devices • Gain settings, low & high • Sound • Threshold • Peak Hold facility
  26. 26. Sreeraj S R Gain settings • On low gain settings the machine will require a greater signal before the output changes - in other words, it is less sensitive. • On higher gain settings, a small amount of EMG activity will be easily seen by the patient.
  27. 27. Sreeraj S R Sound • Most EMG biofeedback devices offer an audible feedback in addition to the visual information • the change in sound is such that the frequency of the ‘beeps’ increases with increased EMG activity.
  28. 28. Sreeraj S R Threshold • Incorporation of a threshold system enables the patient targets to be set. • The audible signal can be adjusted so that it will only be heard if the patient achieves a preset activity level. • to achieve an increase in muscle activity, the threshold can be set so that the audible feedback only comes on when 50% of the scale has been achieved.
  29. 29. Sreeraj S R Peak Hold facility • Some devices offer a peak hold facility which enables either the signal to be fed back on a continuous basis i.e. Peak Hold OFF. • With the Peak Hold ON, the display does not change instantly, but reports the peak activity in the previous 3 second recording period. • This facility can be useful especially in later stage recovery or rehabilitation, when sustained activity is more important than instantaneous EMG spikes. • In early rehabilitation, it is preferable to use the instantaneous feedback as it is far less confusing i.e. Peak Hold OFF.
  30. 30. Sreeraj S R Equipment
  31. 31. Sreeraj S R Electrode Placement • Silver/Silver Chloride construction • judicious electrode placement • electrode spacing • Noise/ movement artefact • active electrodes should be placed in parallel with the dominant muscle fibres
  32. 32. Sreeraj S R Uses • Facilitate muscle contractions • Promote increased motor recruitment • Regain neuromuscular control • Decrease muscle spasm • Promote relaxation
  33. 33. Sreeraj S R Indications • Stroke • Spinal cord injury • Recovering and improving muscle action • Chronic musculoskeletal injury • Pain • Posture control • Balance and mobility • Trunk muscle re education • Respiratory muscle control • Incontinence • Stress related conditions • Hypertension • Idiopathic Raynaud’s disease
  34. 34. Sreeraj S R Contraindications • If the patient is prohibited from moving the joint or isometric contractions, then BF should NOT be used • Unhealed tendon grafts • Avulsed tendons • Third degree tears of muscle fibers • Unstable fracture • Injury to joint structure, ligaments, capsule, or articulating surface
  35. 35. Sreeraj S R Technique for Motor Recruitment • Position pt., Explain to pt., Work in quiet area. • Apply sensors to an area to demonstrate the desired A-V signal and activity. • Adjust to the most sensitive level that picks up any MUAP that pt. can produce • Instruct pt. to try to produce an A-V signal • As voluntary muscle activity improves, the A-V signal will increase. Adjust the gain to decrease the sensitivity, so pt. has to work harder to recruit more muscle units. • As pt. masters in one position, change positions • Document all parameters. Tx duration 30-60 min • Clean up
  36. 36. Sreeraj S R Inhibition of Spasticity • Goal: decrease undesirable muscle activity that may be interfering with functional movement. • Eval. spasticity, Explain to pt., Apply sensors and demonstrate desired activity. • Find the least sensitive setting that produces minimal A- V feedback • Have pt relax, use techniques and have pt. lower the A-V signal. • As the signal decreases, lower the shaping controls (gain), to a more sensitive level. As pt. relaxes better, continue to increase sensitivity • Change positions
  37. 37. Sreeraj S R • A simple device to provide feedback to ensure quality, and precision in exercise performance and testing. • Monitors position of the low back and provides feedback when the abdominal muscles are not actively or effectively protecting the spine.
  38. 38. Sreeraj S R References 1. http://en.wikipedia.org/wiki/Biofeedback 2. http://bme2.aut.ac.ir/~towhidkhah/MotorControl/Resources/EMG.pdf 3. http://www.electrotherapy.org/modalities/biofeed.htm 4. Low & Reed, Electrotherapy Explained, principle and Practice, 4th edition, 2009, Elsevier, 5. Jagmohan Singh, Textbook of Electrotherapy,1st Edition, 2005, Jaypee Publications.