A study of discomfort with electrical stimulation.

The primary purpose of this study was to investigate the influence of personality variables and contractile forces on magnitude estimates of pain unpleasantness and pain intensity during varying levels of neuromuscular electrical stimulation (NMES). Thirty volunteers, according to their scores on a preferred coping-style questionnaire, were assigned to one of two groups, one designated "monitors" (information seekers) and the other designated "blunters" (information avoiders). All subjects were administered varying levels of two types of NMES, one causing both afferent stimulation and muscle contraction and one causing only afferent stimulation. Subjects judged the intensity and unpleasantness of each current type using magnitude estimation. Data were analyzed using a 2 x 2 x 2 x 3 (coping style x current type x pain descriptor x current level) analysis of variance. The results indicated that the rate of increase of magnitude estimates for unpleasantness and pain intensity that corresponded to increases in current were dependent on (1) the preferred coping style of the subject, (2) whether the stimulus caused a muscle contraction, and (3) whether the subject was judging the intensity or the unpleasantness of the applied stimulus. Behavioral styles appear to affect how subjects characterize the discomfort associated with NMES, and involuntary muscle contractions contribute to the discomfort felt from NMES. These results suggest that interventions tailored to a preferred coping style may increase a subject's level of tolerance to NMES and thus provide a more beneficial treatment.