Temperatures were recorded simultaneously: rectal by a mercury thermometer; right leg skin by probe of Nihon Kohden 6000 polygraph; and right leg subcutaneous, intramuscular, and periosteal, and left leg intramuscular temperatures by a fluorooptic biomedical fiber optic (0.6 mm diameter) thermometer connected to a computer system. Total system accuracy was 0.01℃ Cold gel packs were applied for 10, 15, 20, 25, and 30 minutes duration.

The results can be summarized as cooling and rewarming data. 1) The superficial tissues such as skin and subcutaneous demonstrated the most rapid and profound cooling effect. The deeper tissues such as bone and muscle exhibited a smaller and more gradual decline in temperature. 2) There was a prolonged rewarming period in all tissues after the removal of the cold gel pack but this period was longer in deeper tissues. According to cold gel pack application time, the rewarming time in intramuscular layers to baseline or plateau temperatures was about: 60 ± 3 minutes for 10 minutes application, 100 ± 4 for 15, 130 ± 5 for 20, 140 ± 7 for 25, and 145 ± 8 for 30.

It can be concluded from these results that with increased cold gel pack application time, deep tissue temperature decreased and the duration of cooling effect increased. However, the data indicated that the length of application time and the duration of cooling effect were not linearly related. Especially after 20 minutes of application this ratio decreased progressively. There may be implications of these results for clinical practice.