Papers of the Week

Musculoskeletal pain reduces corticomotor excitability (CE) and methods modulating such CE reduction remain elusive. This study aimed to modulate pain-induced CE reduction by performing action observation and motor imagery (AOMI) during experimental muscle pain. Twelve healthy subjects participated in three cross-over and randomized sessions separated by one week. During the AOMI session subjects performed an AOMI task for 10 mins. In the AOMI+PAIN session, hypertonic saline was injected in the first dorsal interosseous (FDI) muscle prior to performing the AOMI task. In the PAIN session, subjects remained at rest for 10 min or until pain-resolve after the hypertonic saline injection. CE was assessed using transcranial magnetic stimulation motor-evoked potentials (TMS-MEPs) of the FDI muscle at baseline, during, immediately after, and 10 min after AOMI and/or PAIN. Facilitated TMS-MEPs were found after two and four mins of AOMI performance (P<0.017) whereas a reduction in TMS-MEPs appeared at four mins (P<0.017) during the PAIN session. Performing the AOMI task during pain counteracted the reduction in CE, as evident by no change in TMS-MEPs during the AOMI+PAIN session (P>0.017). Pain intensity was similar between the AOMI+PAIN and PAIN sessions (P=0.71). This study, that may be considered a pilot, demonstrated the counteracting effects of AOMI on pain-induced reduction in CE and warrants further studies in a larger population. PERSPECTIVE: This is the first study to demonstrate a method counteracting the reduction in corticomotor excitability associated with acute pain and advances therapeutic possibilities for individuals with chronic musculoskeletal pain.