Van Selm, M., Gibson, W., Travers, M., Moseley, L., Hince, D. A., & Wand, B. (2018). Visually-induced analgesia in a deep tissue experimental pain model: A randomised cross-over experiment. European Journal of Pain, Online First.
Background: Visualizing one’s own painful body part appears to have an effect on reported pain intensity. Furthermore, it seems that manipulating the size of the viewed image can determine the direction and extent of this phenomenon. When visual distortion has been applied to clinical populations the analgesic effects have been in opposition to those observed in some experimental pain models. To help resolve this problem we explored the effect of visualisation and magnification of the visual image on reported pain using a delayed onset muscle soreness (DOMS) pain model.
Methods: We induced DOMS in the quadriceps of 20 healthy volunteers. Forty-eight hours later participants performed a series of painful contractions of the DOMS affected muscle under four randomised conditions: 1. Viewing the injured thigh; 2. Viewing the contralateral thigh; 3. Viewing a neutral object; 4. Viewing the injured thigh through magnifying glasses. For each condition, participants rated their pain intensity during a series of painful contractions.
Results: We observed that direct visualisation of the injured thigh had no effect on pain intensity when compared to viewing the contralateral thigh or neutral object. However, magnification of the DOMS-affected leg during the performance of painful contractions caused participants to report more pain than when viewing the injured thigh normally. Conclusions: These results further demonstrate that the effect of visualisation varies between different pain conditions. These results may have implications for the integration of visual feedback into clinical practice.
deep tissue, visualizing pain, pain intensity, delayed onset muscle soreness (DOMS)
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