The Effect of Ultrasound on the Mechanical Pain Threshold of Healthy Subjects

Abstract

The purpose of this study was to examine the effect of ultrasound on threshold to pain produced by a pressure dolorimeter. Twenty healthy, pain-free subjects (12 men, 8 women) who were naive to ultrasound received five minutes of continuous 1.1 MHz ultrasound at 1.0 W/cm2 on the dorsal aspect of one forearm. The other arm acted as the control and received sham ultrasound. A pressure dolorimeter was used to measure pain threshold on the treated area and on an untreated area of both arms, before and after the ultrasound. A three-way ANOVA revealed an interaction among arm (control versus experimental), site (treated versus untreated) and time (before versus after treatment). Newman-Keuls post hoc analysis demonstrated a significant (p < 0.05) increase in pain threshold from before (mean = 1.53 kg/cm2, SE = 0.08) to after (1.93 ± 0.12 kg/cm2) treatment only on the dorsal aspect of the experimental arm. There were no changes in pain threshold on the treated site of the control arm (1.49 ± 0.07 − 1.56 ± 0.08 kg/cm2) or on the untreated site on the experimental (1.95 ± 0.12 − 1.96 ± 0.13 kg/cm2) or control (1.95±0.13 − 1.94±0.13 kg/cm2) arm. It is concluded that, in healthy subjects, continuous ultrasound can raise the threshold of pressure-induced pain. The purpose of this study was to examine the effect of ultrasound on threshold to pain produced by a pressure dolorimeter. Twenty healthy, pain-free subjects (12 men, 8 women) who were naive to ultrasound received five minutes of continuous 1.1 MHz ultrasound at 1.0 W/cm2 on the dorsal aspect of one forearm. The other arm acted as the control and received sham ultrasound. A pressure dolorimeter was used to measure pain threshold on the treated area and on an untreated area of both arms, before and after the ultrasound. A three-way ANOVA revealed an interaction among arm (control versus experimental), site (treated versus untreated) and time (before versus after treatment). Newman-Keuls post hoc analysis demonstrated a significant (p < 0.05) increase in pain threshold from before (mean = 1.53 kg/cm2, SE = 0.08) to after (1.93 ± 0.12 kg/cm2) treatment only on the dorsal aspect of the experimental arm. There were no changes in pain threshold on the treated site of the control arm (1.49 ± 0.07 − 1.56 ± 0.08 kg/cm2) or on the untreated site on the experimental (1.95 ± 0.12 − 1.96 ± 0.13 kg/cm2) or control (1.95±0.13 − 1.94±0.13 kg/cm2) arm. It is concluded that, in healthy subjects, continuous ultrasound can raise the threshold of pressure-induced pain.