Abstract
One prevalent theory is that chronic muscle pain is associated with a regional increase in sympathetic vasomotor activity and decreased intramuscular blood flow. The purpose of this study was to determine the effect of increase in systemic sympathetic outflow induced by cold pressor stimulation on the hemodynamics of human masseter muscle. Hemoglobin concentration, oxygen saturation, heart rate, and blood pressure levels were monitored in 10 healthy, non-masticatory muscle pain subjects. The subjects were instructed to bite at 50% maximum voluntary contraction for 30 seconds with and without cold pressor stimulation. Cold pressor stimulation was applied, by submersing their right upper extremity into a 15°C cold water bath when clenching began (CPT1) or 2 minutes before clenching (CPT2). The post-contraction hyperemia results demonstrated that cold pressor stimulation significantly reduced intramuscular hemoglobin levels within the masseter muscle (p<0.005). On the other hand the oxygen saturation levels were not affected by the cold pressor stimualation paradigm. Systolic pressure and diastolic pressure were also significantly increased by this stimulation, while their heart rate did not change with the stimulation. These hemodynamic changes were very similar to hemodynamic characteristics previously observed in chronic masticatory muscle pain patients reported by Delcanho et al. (1996). This demonstrated that increased sympathetic outflow could be related to the underlying mechanism of chronic muscle pain.
