The purpose of this investigation was to measure energy expenditure and whole body carbohydrate and fat oxidation during shallow water exercise (SWE; submerged to axillary level). The level of energy expenditure and the relative contribution of fuels (e.g., carbohydrate [CHO], fat) depends on the intensity of exercise effort. This descriptive study addressed two questions: (1) what is the energy expenditure of performing SWE over a range of intensities; and (2) how does the rate of CHO and fat usage change with increasingly more demanding SWE efforts. Five healthy females (ages 18 to 26 years) performed five submaximal and one maximal SWE bout based on perceived effort (Borg Scale). Indirect calorimetry (Parvo-Medic metabolic analyzer) was employed to assess metabolic response while heart rate (HR) was monitored via telemetry (Polar technology). For perception of efforts ranging from very light (~50 percent HR peak) to very hard (~88 percent HR peak), the rate of energy expenditure ranged from 3.5+0.7 to 10.5+1.3 kilocalories per minute (Kcal.min-1), while the maximal SWE effort elicited a metabolic response of 13.2+1.7 Kcal.min-1 (~ 10 X resting metabolic rate). From very light to very hard, the rate of CHO oxidation increased from 2.0+1.0 to 9.4+1.8 Kcal.min-1 (~370 percent increase), while fat oxidation remained variable among the SWE efforts. In conclusion, carbohydrate oxidation plays an increasingly more important role as a fuel source during SWE efforts that require a high rate of energy expenditure. Furthermore, this study provides insight into the energy requirements of SWE, a mode of exercise that is becoming more popular
