Habituation to cold-pain during repeated cryokinetic sessions.

Clinicians claim that patients habituate to cold-induced pain during cryokinetic treatments, but this has not heretofore been tested. We treated the right ankle of 38 subjects with a simulated cryokinetic treatment daily for 8 days using either 1 degrees or 5 degrees C water. On days 9 and 10, the right ankle was treated with the opposite temperature and the opposite ankle (left) was treated with the habituation temperature. Cold-induced pain was recorded five times each day (after each ice immersion bout) using Borg's Perceived Pain Scale and the McGill Pain Questionnaire. There was a sharp decrease in pain from days 1 through 5, but no difference between days 5 through 8. Pain during bout one was significantly greater than the following four bouts for all days except day 1. Location of pain changed between days but not between bouts. The instep was the most frequent location of pain for the first 3 days. The choice of "no specific location" increased steadily from day 2 to 8. The number of descriptor terms chosen on the McGill Pain Questionnaire decreased from day 1 to day 8. Exceptions to this were the terms cool, cold, freezing, and numb. Common terms chosen on days 1 through 3 were throbbing, sharp, burning, tingling, hurting, and nagging. On days 9 and 10, pain in the opposite (left) limb was greater than pain at the end of right limb habituation, but similar to day 1 of habituation. Right limb immersion with a lower temperature resulted in greater pain than that perceived on day 8. Daily repeated cryokinetic treatments are sufficient to produce habituation to cold-induced pain. Habituation was specific to the limb treated and temperature of habituation; thus, we conclude it is primarily physiological with some psychological influence. Athletic trainers are justified in telling patients who are undergoing ice water immersion that the cold pain will diminish with repeated applications.