Effects of helium-neon laser irradiation on skin resistance and pain in patients with trigger points in the neck or back

The purpose of this double-blind study was to ascertain the effects of helium-neon (He-Ne) laser irradiation on skin resistance and pain in patients with trigger points in the neck or low back. This study entailed a partial replication of a previ-ous study by Snyder-Mackler and associates that determined the use of the He-Ne laser increased skin resistance overlying a trigger point. Twenty-four patients were randomly assigned to either a treatment or a control group and received three 20-second applications of laser irradiation or placebo "stimulation " respectively. Pretreatment and posttreatment skin resistance and pain measurements (via visual analog scale) were taken during each session. Results indicated a statisti-cally significant increase in skin resistance (p <.001) and a decrease in pain (p <.005) following laser treatment. There was not a significant correlation between skin resistance and pain across subjects. These data substantiate the previ-ous findings of Snyder-Mackler and associates and demonstrate a reduction in pain. Helium-neon laser treatment, therefore, may be an effective adjunct to con-ventional physical therapy of these patients. [Snyder-Mackler L, Barry AJ, Perkins AI, et ah Effects of helium-neon laser irradiation on skin resistance and pain in patients with trigger points in the neck or back. Phys Ther 69336-341, 1989