THE ROLE OF MUSCLE-SPINDLES IN ANKLE MOVEMENT PERCEPTION IN HUMAN-SUBJECTS WITH DIABETIC NEUROPATHY

The objective of this study was to develop a quantitative method to as sess muscle spindle function. Three groups of subjects were studied: t en young and healthy subjects, 15 older subjects with diabetic neuropa thy, and 15 age-matched controls. All subjects performed an ankle-move ment matching task with and without muscle vibration. Input from the p lantar cutaneous mechanoreceptors was minimized by using a foot-clampi ng device. The younger subjects tracked the movement very well, but vi bration had a significant effect on their performance (P < 0.001). Sim ilar results were seen in the older control subjects, but they were le ss successful in tracking movement and slightly less affected by vibra tion. The neuropathic subjects had the most difficulty tracking, and v ibration had only a small but still significant effect on their perfor mance. The interaction between the group and the vibration effect was highly significant (P < 0.001), indicating that the performance of the control subjects changed to a greater degree in the presence of vibra tion than the performance of the subjects with diabetic neuropathy. Mu scle spindles are the primary receptors that are involved in the chang e in tracking performance when vibration is added during an ankle-move ment matching task, and we therefore conclude that the procedure descr ibed provides a quantitative evaluation of muscle spindle function. Th e results demonstrate that diabetic neuropathy degrades muscle sensory function, which may contribute to the impaired balance and unsteadine ss of gait that has been observed in diabetic neuropathy.