• Siobhan M Schabrun, Thorvaldur S Palsson, Tribikram Thapa, and Thomas Graven-Nielsen.
• Western Sydney University, Brain Neuroplasticity and Rehabilitation Unit (BRAiN-u), School of Science and Health, Penrith, NSW, Australia.
• Pain Med. 2018 Mar 1; 19 (3): 608-614.

ObjectiveTo examine the effect of motor activity on the magnitude and duration of altered corticomotor output following experimental muscle pain.DesignExperimental, pre-post test.SettingUniversity laboratory.SubjectsTwenty healthy individuals.MethodsParticipants were randomly allocated to a Rest or Movement group. The Rest group sat quietly without moving for the duration of the experiment. The Movement group repeated a unimanual pattern of five sequential keystrokes as quickly and as accurately as possible immediately following the resolution of pain. Pain was induced into the right extensor carpi radialis brevis muscle by a bolus injection of 0.5 mL hypertonic saline. Corticomotor output was assessed as motor evoked potentials in response to transcranial magnetic stimulation before, immediately after, and at 10, 20, and 30 minutes following pain resolution. Pain intensity was recorded every 30 seconds using an 11-point numerical rating scale.ResultsThere was no difference in peak pain intensity (P < 0.09) or duration (P < 0.2) between groups. Corticomotor output was reduced in both groups (P < 0.002) at 10 minutes (P < 0.002), 20 minutes (P < 0.02), and 30 minutes (P < 0.037) following the resolution of pain relative to baseline. There was no difference between groups at any time point.ConclusionsPerformance of motor activity immediately following the resolution of acute muscle pain did not alter the magnitude or duration of corticomotor depression. Understanding corticomotor depression in the postpain period and what factors promote recovery has relevance for clinical pain syndromes where ongoing motor dysfunction, in the absence of pain, may predispose to symptom persistence or recurrence.

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