Influence of cold water immersion on heat debt and substrate utilization in males varying in body composition: a retrospective analysis

The present article is a retrospective analysis of previously published data. This analysis examined the effect of immersion in 18, 22 and 26 degrees C cold water, on heat debt (kJ), substrate utilization [i.e., R (respiratory exchange ratio) calculated using indirect calorimetry], and aerobic metabolic rate (i.e., VO2 (oxygen consumption) 1 # min(-1)] in 24 male volunteers (20-35 years) given a preexposure meal (60.2 g carbohydrate, 12.0 g protein, and 2.8 g fat at 60 min prior to the experimental trial) and examined during 90 min of immersion to the first thoracic vertebrae. Body composition was determined via underwater densitometry. Subjects were divided with respect to high body fat (HF; 18-22%, n = 12) or low body fat (LF; 8-12%, n = 12) and randomly assigned to one of three water temperatures. Body heat debt and R did not differ between the LF or HF groups, between temperatures, or across time. Percent calories utilized indicated that for these experimental conditions the predominant substrate utilized between the LF and HF groups across time was derived from carbohydrate. In addition, VO2 was greater (p = .0004) in the LF than HF group, and the latter was greater (p = .0013) in the 18 degrees C group versus the 26 degrees C group and increased across time (p = .0001); that is, VO2 after 5 min of immersion was less than at 60 and 90 min, and values obtained after 30 min of immersion were less than those at 90 min of immersion. Based on these data, it appears that the LF group would expend more calories (308.9 vs. 199.9 kcal, respectively) and more likely derive these calories from a carbohydrate source than the HF group during 90 min of cold water immersion. It would appear beneficial to consider a feeding supplement for the low-fat individual if immersion was in a more thermal stressful environment or extended for a protracted period of time.