The aim of this study was therefore to compare the levels of the pro- and anti-inflammatory cytokines IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, TNF, IFN-γ, and GM-CSF in the masseter muscle between TMD myalgia patients and healthy controls and the effects of a repetitive tooth-clenching task on their release and relation to masseter pain intensity, fatigue, and pressure-pain thresholds (PPT). Here, CXCL8 is linked to Myalgia.