BODY SITE VARIATION OF HEAT PAIN SENSITIVITY

Thirty-two healthy human subjects provided thresholds for the percepti on of slight and moderate heat pain. Four body sites were tested bilat erally: thenar eminence of the hand, plantar surface of the foot, dors olateral forearm, and lateral calf. Thresholds for the glabrous skin o f the hand and foot were significantly greater than thresholds for the hairy skin of the arm and leg, the average difference being 1.3 degre es C. Laterality was not a statistically significant factor. Threshold s increased progressively over 2-4 weeks of repeated testing, resultin g in values averaging 0.6 degrees C higher in the later sessions. The difference between moderate and slight pain thresholds averaged 1.1 de grees C, and was consistent across body sites and with repeated testin g. The threshold values were normally distributed across subjects. Con siderable intersubject variability was observed for both slight and mo derate pain thresholds, more so on glabrous than on hairy skin sites. In comparison, the distribution of right-left difference values was na rrower, demonstrating less intrasubject versus intersubject variabilit y. The highly significant difference in thresholds between glabrous an d hairy skin sites demonstrates the importance of skin type for heat p ain sensitivity. In contrast, there was no significant difference in h eat pain sensitivity between comparable sites on the upper versus lowe r extremities, or between left and right sides.