SUMMARYObjectives: The aim of this paper is to give a brief introduction to the mechanisms and manifestations related to muscle hyperalgesia. It has become increasingly evident that muscle hyperalgesia plays an important role in chronic musculoskeletal pain. Better understanding of the involved basic mechanisms and better methods to assess muscle pain in the clinic might provide new possibilities for designing rational therapies and for targeting the pharmacological intervention optimally.Results: Increased muscle sensitivity can be manifested as either 1. pain evoked by a normally nonnociceptive stimulus [allodynia], 2. increased pain intensity evoked by nociceptive stimuli [hyperalgesia], or 3. increased referred pain areas with associated somatosensory changes. For basic experimental studies quantitative sensory testing provides the possibility to evaluate these manifestations in a standardized way in patients suffering from musculoskeletal pain or in healthy volunteers.Conclusions: Increased muscle se...