Group assignments in the current study were determined based on clinical signs of cervical function and impairment as well as symptom status. The data suggest that coupled motions parallel differences between these subject groups (ie, increasing slope with increasing impairment). The variation in ratios we observed for coupled cervical motions relative to palpable findings and diagnostic categories can be attributed to numerous factors. Among these factors are the possibility of local sensory alteration, hyperirritability, changes in tissue texture, and changes in local circulatory patterns. In turn, such “compromised internal environments” affect normal motor function, mechanical properties of muscle, muscle loading factors, force feedback from muscles and tendons, and velocity feedback from spindle receptors. These structural and physiologic factors clearly signal a neural basis for vertebral function and dysfunction, thus affecting the reflex control of motion. Because this control is used to coordinate agonist and antagonist muscular activity to produce smooth and effective motions, diagnoses of functional asymmetry and variation in coupled motion may indicate adaptive motor patterns (functional irregularities) in response to altered reflex function when symmetry no longer exists.