Intensity and character of pain and muscular activity levels elicited by maintained extreme flexion position of the lower-cervical-upper-thoracic spine.

The aim of this study was to find out whether maintained extreme flexion position of the lower-cervical-upper-thoracic spine in a sitting posture could induce pain, and thus possibly play a role in work related disorders with cervico-brachial pain. Ten healthy subjects assessed pain intensity of experimentally-induced pain on a Visual Analogue Scale (VAS). The quality and location of the pain was indicated on a drawing of the body. The load moment induced by the weight of the head-and-neck was calculated. The EMG activity levels were recorded from the splenius, thoracic erector spinae-rhomboid, and descending part of trapezius muscles. This posture, which resembles the posture in some common work, caused pain in all subjects. The pain was experienced within 15 min, increased with time, disappeared within 15 min after the end of provocation, but was again experienced by nine subjects the same evening or next morning and lasted up to four days. The primary location was in the dorsal part of the lower cervical and upper thoracic spine; three subjects also reported pain in the arms and one in the head. The recorded EMG levels were very low, but they increased somewhat during provocation. It is suggested that thorough recordings of work postures should be included in ergonomic analyses to provide a basis for the avoidance of such positions which might provoke pain.