• Tetsurou Torisu, Kelun Wang, Peter Svensson, Antoon De Laat, Yoshihisa Yamabe, Hiroshi Murata, and Lars Arendt-Nielsen.
• Center for Sensory-Motor Interaction (SMI), Laboratory for Human Experimental Pain Research, Aalborg University, Fredrik Bajers Vej 7 D-3, DK-9220 Aalborg, Denmark.
• Clin Neurophysiol. 2008 Dec 1;119(12):2819-28.

ObjectiveTo investigate the effects of soreness evoked by eccentric jaw exercises on two types of brainstem reflexes: the short-latency stretch reflex and the longer-latency exteroceptive suppression (ES), and to test for possible relationships between magnitude of soreness and reflex responses.MethodsThe brainstem reflexes of jaw-closing muscles were recorded before (Baseline), immediately after (Post-task), and 1 day after (1-day-after) a 30-min eccentric exercise in 15 healthy men. All subjects participated in a control session without exercise.ResultsSoreness sensations at rest and during maximum biting were significantly elevated until 1-day-after the eccentric exercise (P<0.014). The ES responses tended to be increased (more inhibition) at Post-task and 1-day-after. There was a significant correlation between the ES response and the soreness sensation during maximum biting (P<0.04). The jaw-stretch reflex did not show significant change after the eccentric exercise.ConclusionsMuscle soreness associated with eccentric jaw exercises has a differential impact on the jaw-stretch reflex and the ES response.SignificanceExperimentally induced acute muscle pain has previously been shown to influence both the ES and the jaw-stretch reflex, thus, different types of muscle pain and symptoms can be speculated to have different effects on a variety of brainstem reflexes.

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