The effect of two sites of high frequency vibration on cutaneous pain threshold.

The purpose of this study was to evaluate the effect of two sites of high frequency vibration on experimentally produced pain thresholds. Subjects were assigned to one of two experimental groups. Vibration was applied proximal to the site of pain threshold measurement in one group and distal to the measurement site in the other group. The cutaneous pain threshold was measured at the ulnar aspect of the wrist in both groups prior to, during, and following 5 min of vibration. Subjects were 30 right-handed, Caucasian males with a negative history of upper extremity dysfunction. A repeated measures analysis of variance (ANOVA) was used to analyze the data. There was a significant interaction between vibration site and time of pain threshold measurement. Post hoc analysis of that interaction indicated that a significant difference between experimental groups occurred only during vibration; the distal group values were significantly higher than the proximal group values (P less than 0.03). For the distal group, pain threshold values were significantly higher during vibration than pre vibration and post vibration (P less than 0.05). In the proximal group, there was no significant difference in pain threshold values across the 3 time periods. The results of this study indicate that vibration applied distal to the site of pain can provide temporary analgesia.