A RELIABLE METHOD FOR SUSTAINING A PREDEFINED PRE-INNERVATION LEVEL

Numerous experimental approaches are based on evaluating electromyogra phically recorded muscle activity. Some experiments require a certain level of pre-innervation in a muscle or muscle group whereas others mu st avoid this. Measured parameters, such as the time to onset of the m uscle response to an electrical stimulus, etc., depend critically on t he level of pre-innervation. The pre-innervation level is most commonl y estimated from parameters such as the force generated by this muscle or the upright posture of a human subject. These methods, however, ar e indirect and may yield erroneous results. This paper describes an in expensive method developed for a wide range of applications in muscle- tonus-based experiments, in which the tonus is precisely controlled. A simple electronic circuit is presented by which the level of muscle p re-innervation is directly recorded, monitored and - depending on the experimental approach - also fed back to the subject. Physiological ex periments on the flexion reflex in healthy human subjects document the reliability of our electronic device.