DISCUSSION
acute pain, pain, lower limb pain, upper limb pain, depression, motor skill learning
This was the first study to explore the variability of corticomotor reorganization in response to sustained lower limb pain. Corticomotor responses were variable, with 46% of participants displaying corticomotor facilitation, 46% displaying corticomotor depression, and 8% being considered nonresponders based upon map volume. Further investigation of this variability revealed that corticomotor facilitation was strongly correlated with greater mechanical sensitivity (lower PPTs). Corticomotor depression was correlated with lower mechanical sensitivity (higher PPTs), suggesting a potentially protective response. Corticomotor reorganization was not associated with changes in pain intensity (numerical rating scale) or function. These data provide novel insights into the potential mechanisms underlying recurrent hamstring pain and injury.The variable corticomotor changes observed in response to sustained hamstring pain are consistent with those reported in studies of the upper limb. A recent systematic review and meta‐analysis of 90 data points across five studies demonstrated that, relative to baseline, 57% of data points taken during sustained pain reflected decreased corticomotor excitability and 43% reflected increased excitability. Such variability in corticomotor responses is congruent with that observed following both motor skill learning (Cavaleri et al., The relationships between corticomotor outcomes and mechanical sensitivity observed in the present study contrast with that observed in studies of sustained upper limb pain. Previous work has demonstrated that corticomotor depression is associated with reduced upper limb pain severity during pain lasting minutes‐to‐hours but increased pain severity during sustained pain (lasting days‐to‐weeks) (Chowdhury et al., The present study extends existing literature by demonstrating that, in contrast to findings from upper limb studies, corticomotor depression may represent a beneficial response during sustained hamstring pain. However, it is important to note that, although corticomotor depression was associated with improved mechanical sensitivity, no such relationship was observed in terms of pain intensity (on a numerical rating scale). The reason for this discrepancy is unclear, but it should also be noted that PPTs reflect a distinct mechanism in peripheral neural sensitivity, whereas pain intensity is a subjective report that may encapsulate a greater degree of psychosocial influences. Indeed, previous work has demonstrated that pain intensity is not necessarily correlated with areas of increased mechanical sensitivity in the lower limb (Sánchez Romero et al., It is reasonable to postulate that corticomotor adaptations to pain could be region‐specific. The upper limb is responsible for fine motor tasks, so a reduction in corticomotor excitability during acute pain in this region is thought to be beneficial as a means of restricting movement and ensuring protection from further harm (Cavaleri et al., 