['Contrast therapy has a long history of use in sports medicine. Edema and ecchymosis reduction, vasodilation and vasoconstriction of blood vessels, blood flow changes, and influences on the inflammatory response are physiologic effects attributed to the ability of this modality to evoke tissue temperature fluctuations. Our purpose was to measure the change in human gastrocnemius intramuscular tissue temperature during a typical contrast therapy treatment.', 'A randomized-group design was used to examine differences between 2 groups of subjects following a 31-minute warm whirlpool (control) and a 31-minute contrast therapy (experimental) treatment. A hydrotherapy room in a small- college sports medicine facility served as the test environment.', 'Twenty (7 females and 13 males) healthy college students (age = 20.9 +/- 1.2 years; ht = 178.5 +/- 11.1 cm; wt = 79.2 +/- 21.7 kg) volunteered to participate in this study. Subjects were randomly assigned to either a control or a treatment group.', 'Intramuscular tissue temperatures in the gastrocnemius were recorded every 30 seconds.', 'There was a significant difference in mean overall temperature change between the experimental group (0.85 degrees C +/- 0.60 degrees C) and the control group (2.10 degrees C +/- 1.50 degrees C). In addition, there were significant differences between the 2 groups at 10, 15, 16, 20, 21, 25, 26, 30, and 31 minutes. At each recording point, the control group temperature change was significantly higher than that of the experimental group. There was no difference in absolute temperatures at the 11-minute recording point between the groups.'] Does contrast therapy cause fluctuations in human gastrocnemius intramuscular temperature?