Pressure pain thresholds in normal muscles: reliability, measurement effects, and topographic differences.

This project sought to determine measurement effects, topographic variability, and reliability of pressure pain thresholds (PPT) as an index of normal tenderness in the masseter and temporalis muscles of non-patient subjects. PPTs were measured using the ascending method of limits in 10 subjects. The PPT over 5 trials at each of 5 temporalis sites and 10 masseter sites was measured in 1 experiment. Interpretation of the data with repeated measures analysis of variance indicated that the PPT was significantly higher in the temporalis than in the masseter; additionally, the PPT at a tendon area was significantly higher than at the belly area. These differences should be considered in reducing unwanted variability in PPT measures, receptor distribution, and in inference based on patient examination. There were no differences in the PPT over 5 trials and, thus, no measurement effects. The mean of the first 2 trials at each site appeared to give a better estimate of the PPT than the data from either the first trial or second trial alone from that site. In a second experiment, the PPT was measured in 2 trials at each of 4 sites over 5 sessions. The between-session PPT across multiple sessions was reliable and without differences.