Fully rectified, integrated, band (FRIB-) EMG analysis in quantifying muscle activity. Development of a new field equipment.

A new approach for the study of muscular activity applicable in field and laboratory conditions has been developed. The instrument is portable (375 g) and battery operated. The signals are obtained through a surface electrode attached to the skin above the muscle. A reference electrode is applied to a bony area close by. The third electrode, to remove 50 Hz disturbance, is attached at a distance from the muscle to be registered. A time domain band EMG signal is fully rectified and integrated. The isolation of the device is done with an optocoupler. The EMG activity to be thus registered is not hampered by other external or internal (ECG) electrical signals. The recordings can also be made when the person is working quite freely. The recorded values correlate linearly (up to r = 0.99) with the load of the muscle. The angular coefficients obtained with different loads correlate inversely with the strength of the persons. When muscle fatigue develops during a static loading, the registered EMG tends to decrease while simultaneously oscillating. During the recovery from the fatigued state the response to intermittent loadings indicates that the electrical activity pattern varies with time. With the method developed it is possible to detect locally increased electrical activity at rest or during muscle function testing, and it permits the followup of therapeutic measures.