Electromyography - Find out more

Introduction

Increasingly, EMG is being used to assist the therapist to diagnose and treat patients with a wide variety of conditions, and for Patients themselves to improve from the visual and audible biofeedback EMG provides. Up until recently there has been little equipment available on the market for the therapist and patient to choose from at an affordable cost. The NeuroTrac™ ETS and Simplex resolves these problems.

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Background ?
Muscle Training and Relaxation
Applications
Contra Indications

Definition

A test that measures muscle response to nervous stimulation (the electrical activity within muscle fibers).

Background Information

The history of biofeedback EMG is summarised by Yates (1980).  The systematic study of biofeedback began in the 1960's with attempts to train voluntary control of autonomic functions such as heart rate and blood pressure.  It was suggested that so-called involuntary bodily responses could be trained with the same reinforcement procedures as used in training a circus dog to jump through a hoop.  The exciting possibility of gaining voluntary control over bodily functions, particularly those which underline emotional responses, ensured the interest of psychologists in biofeedback.

Biofeedback (EMG) training in physical medicine is a form of skill training; skeletal muscles are trained using knowledge of results, i.e. feedback, to correct action and improve skill.  The initial aim of the training programme is to encourage the patient to make use of the biofeedback signal to modify his or her behavior.  The rationale for biofeedback training is that sensory channel, usually vision or hearing or both, is used to calibrate the cerebral representation of skill when proprioception is impaired.  Herman (1973) postulated two neural sensory channels, one an intrinsic central control loop eliciting signals of predicted or intended movement, the other an extrinsic peripheral control loop eliciting signals of actual movement.  If the extrinsic proprioceptive loop is impaired, as Harris (1971) has postulated for at least some types of cerebral palsy, then the rationale for biofeedback training is that it provides the information needed to calibrate the intrinsic loop, thereby improving motor control.

The major impact of biofeedback for the physiotherapist has been in the use of EMG.  The most prolific writer being Basmajian 1963, 1972 Basmajian et al, 1975.  He reports the use of the EMG to measure the electrical activity associated with the contraction of skeletal muscle and to display this precise information to the patient.  From these beginnings biofeedback training has now come to refer to any technique by which an aspect  of an individual's physical functions, such as joint angle, body position and weight borne through the heel of the foot, is measured continuously and displayed visually and or audibly to the patient.  For example, the frequency of an auditory feedback signal may be proportional to the amount by which a threshold value of the measured variable is exceeded.

Muscle Training and Relaxation

EMG gives the patient feedback concerning the state of tension to relaxation of his or her muscles.  A set of electrodes is placed on the skin over the chosen muscle or muscle group to detect the electrical signals associated with muscle contraction.  The signal from the electrodes is amplified to give some feedback to the wearer.  By providing a visual and or auditory feedback signal which varies in proportion to the amount of electrical activity measured in microvolts (RMS), one can re-educate muscles (Basmajian et al, 1975; Wolf 1997, Wolf et al, 1979) by increasing the activity of weak muscles or relaxing muscles subject to spasm, thereby increasing control and range of movement (Kukulka and Basmajian, 1975).

Applications

• Incontinence
• Patella femoral pain (aqua and land)
• Pelvic floor pain
• Lower back pain
• Neck and shoulder girdle pain
• Neuro feedback
• Phantom limb pain
• Post-traumatic stress disorders
• Repetitive strain injury
• Asthma
• Chronic tension headaches
• Stroke
• Carpal tunnel syndrome
• Posture training
• Spirits injuries
• muscle strengthening
• Facial Palsy

Please review the clinical feedback section of this web site for more information relating to applications of NeuroTrac™ products with EMG.

Contra Indications of EMG