Movement-related skin strain associated with goal-oriented lip actions

It is generally accepted that sensory input contributes to the generation of natural movements. In most motor systems, muscle spindles, tendon organs, joint receptors, and cutaneous mechanoreceptors may provide proprioceptive information. However, the perioral area of the human face lacks muscle spindles, tendon organs, and joint receptors and is therefore a model system for the study of cutaneous afferent contributions to proprioception. This investigation examined a series of skin strains associated with lower-lip movements in human subjects to determine if such strains, which serve as stimuli for cutaneous mechanoreceptors, may underlie proprioception in the face. The results suggested that strains associated with lower-lip movements were of sufficient magnitude to elicit cutaneous mechanoreceptor discharge, as shown in recent human microneurographic studies. Further, the magnitude of multiple strains was predictive of lower-lip movement endpoints. These results highlight the potential importance of cutaneous mechanoreceptors as putative proprioceptors.