Thermal and metabolic responses to cold-water immersion at knee, hip, and shoulder levels

To examine the effect of cold-water immersion at different depths on thermal and metabolic responses, eight men (25 yr old, 16% body fat) attempted 12 tests: immersed to the knee (K), hip (H), and shoulder (Sh) in 15 and 25 degrees C water during both rest (R) or leg cycling [35% peak oxygen uptake; (E)] for up to 135 min. At 15 degrees C, rectal (Tre) and esophageal temperatures (Tes) between R and E were not different in Sh and H groups (P > 0.05), whereas both in K group were higher during E than R (P < 0.05). At 25 degrees C, Tre was higher (P < 0.05) during E than R at all depths, whereas Tes during E was higher than during R in H and K groups. Tre remained at control levels in K-E at 15 degrees C, K-E at 25 degrees C, and in H-E groups at 25 degrees C, whereas Tes remained unchanged in K-E at 15 degrees C, in K-R at 15 degrees C, and in all 25 degrees C conditions (P > 0.05). During R and E, the magnitude of Tre change was greater (P < 0.05) than the magnitude of Tes change in Sh and H groups, whereas it was not different in the K group (P > 0.05). Total heat flow was progressive with water depth. During R at 15 and 25 degrees C, heat production was not increased in K and H groups from control level (P > 0.05) but it did increase in Sh group (P < 0.05). The increase in heat production during E compared with R was smaller (P < 0.05) in Sh (121 +/- 7 W/m2 at 15 degrees C and 97 +/- 6 W/m2 at 25 degrees C) than in H (156 +/- 6 and 126 +/- 5 W/m2, respectively) and K groups (155 +/- 4 and 165 +/- 6 W/m2, respectively). These data suggest that Tre and Tes respond differently during partial cold-water immersion. In addition, water levels above knee in 15 degrees C and above hip in 25 degrees C cause depression of internal temperatures mainly due to insufficient heat production offsetting heat loss even during light exercise.