The relationship between hyperactivity of the head and neck muscles and the pain experienced in tension headache was assessed by comparing the subjective effects of voluntary frontal muscle contraction on self-reports of pain in chronic tension headache patients and in normal volunteers.
Ten tension headache patients and ten volunteers were taught to increase their frontal muscle tension over 10 μvolts through biofeedback and, on three occasions, were asked to maintain that level for periods of one, two or five minutes consecutively.
No difference in EMG levels were observed between patients and control either during baselines, contraction periods or subsequent resting phases. In contrast, headache patients reported more pain immediately and ten minutes after the contraction periods. The longer contraction periods were associated with higher pain intensity score, while the EMGs of the subsequent resting phases were lower. This occurred in both groups.
These results suggest that chronic tension headache patients are more prone to experience pain than normal volunteers with contraction of frontal muscles, in spite of the fact that EMG levels do not differ. A different pain threshold to muscle tension could be responsible for those differences.