Effect of vibratory stimulation on experimental and clinical pain.

The effect of vibratory stimulation on experimental pain of the skin overlying the right and left extensor carpi radialis longus muscle induced by electrical stimulation was studied in 16 healthy subjects and in 18 patients suffering from chronic epicondylalgia of the right elbow. In the healthy subjects there were no side differences whereas in the patients, the skin pain threshold over the painful right muscle was lower than that on the left unaffected side under resting conditions. After vibratory stimulation, the skin pain threshold increased bilaterally by 1.1-1.6 times the pre-stimulation threshold in the healthy subjects and by 1.2-2.3 times this threshold in the patients. In 8 of the healthy subjects there was an increase in peripheral blood flow during stimulation and in 8 there was a small decrease. In 13 patients the change in pain threshold was seen in phase with the local increase and peripheral decrease in peripheral blood flow. In all individuals, the pain thresholds were regained within 45 min of cessation of stimulation. This was in contrast to the general subjective pain in the patients; 12 patients reported that the relief of pain lasted for a period of 1-7 hours.