Moving differently in pain: a new theory to explain the adaptation to pain.

People move differently in pain. Although this statement is unquestioned, the underlying mechanisms are surprisingly poorly understood. Existing theories are relatively simplistic, and although their predictions are consistent with a range of experimental and clinical observations, there are many observations that cannot be adequately explained. New theories are required. Here, we seek to consider the motor adaptation to pain from the micro (single motoneuron) to macro (coordination of whole-muscle behaviour) levels and to provide a basis for a new theory to explain the motor changes in pain.