1. Biofeedback
Chapter 7

2. Biofeedback
Electronic or electromechanical instruments that accurately measures, processes, and provides feedback via auditory or visual signals
Used to help patient develop greater voluntary control of either
Neuromuscular relaxation, or
Muscle re-education following injury

3. Role of Biofeedback Intrinsic feedback = movement
Kinesthetic, visual, cutaneous, vestibular, and auditory signals
Extrinsic feedback = knowledge
Results presented verbally, mechanically, or electronically to indicate the outcome of some movement performance

4. Role of Biofeedback Feedback is ongoing
Occurs before, during, and after any motor or movement task
Feedback from some measuring instrument which provides moment-to-moment information about a biologic function is referred to as biofeedback

5. Role of Biofeedback
Patient able to make appropriate, small changes in performance which are immediately noted and rewarded
Eventually larger changes, or improvements, in performance can be accomplished
Goal = train patient to perceive changes without the use of a biofeedback unit

6. Biofeedback Instruments
Measure electromyographic activity (EMG) indicating amount of electrical activity during muscle contraction
Most common type of biofeedback used in athletic training

7. EMG Biofeedback
Nerve fiber conducts an impulse to the neuromuscular junction where acetylcholine binds to receptor sites on the sarcolemma inducing a depolarization of the muscle fiber
Changes in electrochemical potential difference associated with depolarization can be detected by an electrode placed in close proximity

8. Measuring Electrical Activity
EMG does not measure muscle contraction directly
Measures electrical activity associated with muscle contraction
Units of measure are microvolts
1 volt = 1,000,000 µV
EMG readings may be compared only when the same equipment is used for all readings

9. Measuring Electrical Activity
EMG biofeedback unit receives small amounts of electrical energy generated during muscle contraction (via the electrodes)
Separates or filters electrical energy from other extraneous electrical activity on skin
Amplifies the EMG electrical energy and converts it to some type of information which has meaning to the patient
Meter, auditory signal, light display

10. Anatomy of EMG Biofeedback

11. EMG Electrodes Skin surface electrodes
Some electrodes permanently attach to cable wires while others may snap onto the wire
Some units include a set of three electrodes pre-placed on a velcro band which attaches to the skin

12. EMG Electrodes Size of electrodes varies
4 mm diameter for small muscle activity
12.5 mm diameter for larger muscles
Increasing the size of the electrode will not cause an increase in the amplitude of the signal
Electrodes may be disposable or non-disposable
Require some type of conducting gel

13. EMG Electrode Placement
Prepare skin by scrubbing with an alcohol-soaked prep pad
Electrodes should be placed as near to the muscle being monitored as possible
Electrodes should be parallel to the direction of the muscle fibers
Spacing of the electrodes is critical to reduce extraneous electrical activity (noise)

14. Separation and Amplification of EMG Activity
2 active electrodes
1 reference electrode
Active electrodes pick up electrical activity from motor units firing in the muscles beneath the electrodes

15. Converting EMG Activity to Meaningful Information
Biofeedback units generally provide either visual or auditory feedback relative to the quantity of electrical activity
Visual feedback uses lights, bars, or analogue or digital meters
Auditory feedback uses increasing or decreasing tones, buzzing, beeping or clicking

16. Setting Sensitivity Sensitivity may be set at…
1 µV, 10 µV, or 100 µV
A high sensitivity means the biofeedback unit is sensitive enough to detect the smallest amounts of electrical activity
Higher sensitivity levels should be used during relaxation training
Lower sensitivity levels should be used during muscle re-education training

17. Clinical Applications
Muscle re-education
Isometric contractions sustained for 6-10 sec
Maximize feedback
Tx time = 5-10 min
Relaxation of muscle guarding/Pain control
Concentrate on muscle relaxation
Minimize feedback
Change positions

18. Indications:
Muscle re-education
Regaining neuromuscular control
Increasing isometric/isotonic strength
Relaxation of muscle spasm/guarding
Pain reduction
Psychological relaxation
Contraindications:
Any musculoskeletal condition in which a muscle contraction may exacerbate the condition