An increased response to experimental muscle pain is related to psychological status in women with chronic non-traumatic neck-shoulder pain

Nineteen women with chronic non-traumatic neck-shoulder pain but without simultaneous anatomically widespread clinical pain (NSP) and 30 age-matched pain-free female control subjects (CON) participated in the study.NSP had lower pressure pain thresholds over the trapezius and over the tibialis anterior muscles and experienced hypertonic saline-evoked pain in the tibialis anterior muscle to be significantly more intense and locally more widespread than CON. More intense symptoms of anxiety and depression together with a higher disability level were associated with increased pain responses to experimental pain induction and a larger area size of the clinical neck-shoulder pain at its worst.These results indicate that central mechanisms e.g., central sensitization and altered descending control, are involved in chronic neck-shoulder pain since sensory hypersensitivity was found in areas distant to the site of clinical pain. Psychological status was found to interact with the perception, intensity, duration and distribution of induced pain (hypertonic saline) together with the spreading of clinical pain. The duration and intensity of pain correlated negatively with pressure pain thresholds.Neck shoulder pain remains a major problem in work tasks with high exposure to awkward working positions, repetitive movements and movements with high precision demands. The trapezius muscle is considered particularly affected. The prevalence of chronic neck-shoulder pain appears to be higher in women than in men [1,2]. It causes high socioeconomic costs and significant loss of quality of life for the individual [3]. Because of limited knowledge of the mechanisms involved in transition from acute to chronic pain, attempts to develop effective treatments have had limited success. The clinical manifestations of chronic pain conditions include both somatic (e.g., sensory disturbances, facilitated pain responses in association with movements, tense muscles with hyperalgesia for mechanical