Fat utilization enhanced by exercise in a cold environment

To study substrate utilization during cold temperature exercise, seven men dressed in shorts, T-shirts, and light gloves performed 60 min of continuous cycle ergometer exercise at -10 degrees C and 22 degrees C. The workload at both temperatures represented 66% of the cycle-measured maximal heart rate. Oxygen consumption and respiratory exchange ratio (RER) were measured at rest and during 60 min of exercise. Rates of total and fat energy utilization (kJ X min-1) during exercise were calculated from VO2 and RER. A two-factor repeated measures analysis of variance indicated that at rest oxygen consumption averaged 56% higher and RER 5% lower at -10 degrees C. During exercise, oxygen consumption averaged 10% higher (P less than 0.05), and RER averaged 2% lower (P less than 0.05) at -10 degrees C. The rates of total energy use (mean +/- SD = 39.3 +/- 1.2 vs 35.7 +/- 1.3 kJ X min-1; P less than 0.05) were significantly higher at -10 degrees C than at 22 degrees C. In addition, the rate of fat use increased significantly in both groups after 30 min of exercise. The cumulative total energy expenditure for 60 min of exercise was 13% higher (2379 +/- 308 vs 2110 +/- 415 kJ; P less than 0.05 and the cumulative fat expenditure was 35% higher (979 +/- 209 vs 724 +/- 184 kJ: P less than 0.05) in the cold environment. These results indicate that a cold environment can significantly enhance fat utilization during endurance exercise.