Search

Ten healthy human male subjects with a mean age of 21 years performed negative and negative/positive work with the jaw muscles for about 21 min. The average amount of negative work was 13.3 kgm, while that of negative/positive work was 48.5 kgm. Eight subjects developed either spontaneous or provoked facial pain subsequent to the exercise. No positive correlations were demonstrated between the total number of facial pain sites and the amounts of work and power of the muscles, nor between the number of pain sites and the speed of mandibular movement. It is suggested that the appearance of facial pain was associated with the pre-experimental strength and conditioning of the jaw muscles.

Fatigue was developed by four human subjects after negative work, and by two subjects after negative/positive work by the jaw muscles. Another four subjects did not develop fatigue subsequent to muscular exercise. In subjects with fatigue, the ability to perceive and/or produce repetitively a predetermined mandibular posture, i.e. mandibular kinesthesia, was impaired by about 285%. It is suggested that the distorted kinesthesia resulted from either a fatigue-induced failure of, or a fatigue-induced persistence of, jaw muscle fibers to contract, which in turn led to distorting flows of afferent impulses from muscles spindles and/or tendon organs.

The possible kinesthetic function of proprioceptors in the lateral pterygoid muscle was clinically assessed after anesthesia of muscle and temporomandibular joint receptors, respectively. A mandibular posture was actively and repetitively produced with an average accuracy of 2.5 mm, while the accuracy decreased by about two-fold after narcotization. It is suggested that muscle spindles in the lateral pterygoid muscle as well as mechanoreceptors in the temporomandibular joint capsule are active in the perception and/or control of mandibular postures.