Daytime trapezius muscle activity and shoulder-neck pain of service workers with work stress and low biomechanical exposure

Aim The study aims to look for an association between trapezius muscle activity and shoulder-neck pain in work situations characterized by work stress and low biomechanical exposure. Methods Female subjects (n = 93) were recruited from four occupational groups: health care, shop assistants, banking, and university secretaries. Thirty-eight workers were interviewed and classified as pain-afflicted by their shoulder-neck pain score in the last 6 months; 55 were pain-free. Shoulder-neck pain, bodily state of tension and fatigue, and subjective exposure assessments were monitored by repeated hourly measurements over 24 hr. Trapezius muscle activity was recorded bilaterally by surface EMG. Results Shoulder-neck pain, perceived tension, work stress ("stressful environment"), and mental fatigue was augmented over the workday and reduced leisure time. Physical fatigue was low and stable. Thus, work stress appeared to be the dominant exposure associated with shoulder-neck pain. Muscle activity was low and similar for pain-afflicted and pain-free subjects during working hours. It was unchanged from work to leisure for the pain-afflicted workers and was significantly reduced for the pain-free group. Conclusions Stress-induced shoulder and neck pain is not necessarily associated with elevated trapezius muscle activity, but pain-free workers may benefit from better muscle relaxation in leisure. (C) 2002 Wiley-Liss, Inc.