Diurnal variation of pain perception and heart rate in the human tourniquet pain model in healthy volunteers

The diurnal variation of pain threshold was studied in 13 healthy volunteers (age: 21 - 27 ys) using the tourniquet pain model. A tourniquet was inflated above systolic blood pressure for 1 minute and pain scores and heart rate were recorded at 0.5, 1.0, 1.5 and 2.0 minutes. The test was repeated during a study day at 6.00 h, 12.00 h, 18.00 h and 24.00 h. Significant differences of pain scores between clocktimes were found 1 minutes after inflation and after 1.5 minutes with regard to heart rate. Generally, the highest pain scores were found at 24.00 h.