The overall (± SEM) mean relative Pressure Pain Threshold (PPT) or Pressure Pain Tolerance (PPTol) for each day (N = 14). There was a trend in PPT values in both muscles and PPTol values in the temporalis muscle to increase due to repeated measurement during each daily session, which resulted in mean overall values that exceeded 100% on all 5 days during placebo intervention. The masseter muscle PPT and PPTol measured on Day 2 and 3 were both significantly decreased compared to Day 1 (#: P < 0.05), but this difference occurred independent of intervention. The masseter muscle PPT was, however, significantly lower after monosodium glutamate (MSG) ingestion than after placebo ingestion on Day 2 and 5 (*: P < 0.05). There was no effect of intervention or day on the PPT and PPTol measured from the temporalis muscle.