It has long been assumed that the origin of pain in 'muscle-contraction headache' lies in the peri-cranial muscles, especially in the frontales. Pain, it is assumed, is experienced when the muscles are in spasm. It is further assumed that learned reductions in muscle tone between headache episodes will reduce the probability of future pain episodes.

In this experiment, details are given of EMG measures made on the frontal, occipital, and neck muscles of separate groups of migraine and tension headache subjects. The measures were made before the onset of head pain and later when the same subjects reported pain. As part of the experiment, subjects were exposed to an experimental stressor during the pain-free period, and these results were compared with those of a group of non-headache subjects. Results showed that the headache groups did not differ on any of the pre-headache measures. Neck muscle levels varied markedly when compared with control subjects who had comparatively low levels reactive to an experimental stressor. When the data taken during the headache phase were analysed according to diagnosis, the occipital muscle output was found to be significantly lower in the migraine group and higher in the tension group.