Changes in EMG power spectra during fatigue in muscle contraction and migraine headache patients

Muscle contraction headaches are assumed to be associated with relative ischemia in head muscles due to sustained contractions of these muscles. The present study examined whether an abnormally high degree of relative ischemia occurs during such contractions which were experimentally induced in various types of headache patients. Sustained fatiguing contractions at 50% of the maximum EMG amplitude were carried out in the frontalis, corrugator supercilii, and temporalis muscles. The rate of change of the power spectrum of the surface EMG was measured during the contractions. This measure may be considered as an indirect indication of the degree of relative ischemia. Patients with muscle contraction headaches, migraine, or mixed muscle contraction‐migraine headaches did not show a faster spectral shift in any of the three muscles than a group of non‐headache control subjects. Muscle contraction and mixed headache patients even showed significantly slower spectral shifts in the frontalis muscle. These results suggest that muscle contraction headaches are not associated with an abnormally high degree of relative ischemia during the sustained contractions which are believed to underlie this type of headaches.