AMBULATORY ELECTROMYOGRAM ACTIVITY IN THE UPPER TRAPEZIUS REGION - PATIENTS WITH MUSCLE PAIN VS PAIN-FREE CONTROL SUBJECTS

Study Design. This study compared the ambulatory electromyogram activi ty of persons reporting pain in the shoulder and cervical regions with an equal group of persons not reporting such pain. Ambulatory electro myogram data were obtained over 3-day periods. In addition, all partic ipants completed several standard psychological questionnaires. Object ives. The results were analyzed with inferential statistics to determi ne whether subjects reporting significant pain in the shoulder and cer vical regions had greater ambulatory electromyogram activity than an e qual number of subjects not reporting pain. Summary of Background Data . Considerable controversy exists regarding the role of muscle activit y in the etiology and maintenance of muscle pain disorders. Given the availability of ambulatory recording devices that can provide a detail ed record of muscle activity over an extended period of time, the pres ent research was conducted to determine whether persons reporting shou lder and cervical pain could be differentiated from a group of normal subjects. Methods. All subjects (N = 20) completed a battery of tests with standardized psychometric instruments and then were fitted with a mbulatory electromyogram monitors to record electromyographic activity of the upper trapezius region of the dominants side; the time, durati on, and amplitude of electromyogram activity greater than 2 mu V was r ecorded. The monitors were worn during normal working hours (mean, 6.2 hours per day) over 3 consecutive days, In addition to wearing the mo nitors, all subjects completed hourly self-ratings of perceived muscle tension during the recording periods. Results. As expected, subjects with muscle pain reported significantly more pain (mean, 4.9) than did the normal control subjects (mean, 0.9), t(15) = 3.29, P < 0.01. Howe ver, patients with muscle pain did not have greater average electromyo gram activity (mean, 6.4 mu V) over the 3-day period as compared to th e normal controls (mean, 7.1 mu V), t(18) = 0.25, P < 0.80. Self-monit oring of perceived muscle tension also did not reveal differences betw een pain subjects and the normal control subjects (P < 0.75). Conclusi ons. Ambulatory measurements of electromyogram activity did not differ entiate persons reporting upper trapezius or cervical pain from those that did not report such pain. Persons reporting pain are also not dis tinguishable from normal control subjects on a variety of self-report measures. These results raise questions regarding the role of ambulato ry electromyogram recordings in the evaluation and treatment of muscle pain disorders.