Biofeedback Chapter 7

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

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

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

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

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

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

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

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

Anatomy of EMG Biofeedback

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

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

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)

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

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

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

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

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