A reliable method for sustaining a pre-defined pre-innervation level.

Numerous experimental approaches are based on evaluating electromyographically recorded muscle activity. Some experiments require a certain level of pre-innervation in a muscle or muscle group whereas others must avoid this. Measured parameters, such as the time to onset of the muscle response to an electrical stimulus, etc., depend critically on the level of pre-innervation. The pre-innervation level is most commonly estimated from parameters such as the force generated by this muscle or the upright posture of a human subject. These methods, however, are indirect and may yield erroneous results. This paper describes an inexpensive 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 pre-innervation is directly recorded, monitored and – depending on the experimental approach – also fed back to the subject. Physiological experiments on the flexion reflex in healthy human subjects document the reliability of our electronic device.