AN EXPERIMENT IN MAINTAINING HOMEOSTASIS IN A LONG DISTANCE UNDERWATER SWIMMER.

A record-holding long distance underwater swimmer served as the subject for investigations of conditions of prolonged submersion and exercise. The studies were performed while the swimmer was attempting to swim 110 miles along the Eastern Coast of Florida within a period of approximately 48 hours. The purpose of this experiment was to measure and attempt to replace his metabolic loss. The air was supplied from a selfcontained underwater breathing apparatus SCUBA. His nutritional needs were supplied by the every one-half hour feeding of 125 ml. of a nutrient formula taken down to the swimmer in a nursing bottle. This replacement diet consisted of 18 percent protein, 72 percent carbohydrate and 10 percent fat. The rate of sodium and potassium administration was 4 and 9 mEq. per hour, respectively. The estimates of his caloric requirement were made on the basis of a series of swimming pool trials and found to be approximately 150 kilocalories at a swimming speed of 0.9 mph. The caloric consumption during the ocean swim was calculated from the subjects air usage rate to be 264-280 kilocalories per hour at a swimming speed estimated to be 1.0-1.2 mph. Becuase his caloric replacement was at the rate of 187 kilocalories per hour, the subject had a calculated caloric deficit of 77-93 kilocalories per hour. His weight loss, however, was limited t to 210 gm. Serum and urine changes which occurred during the ocean swim suggested a salt and water diuresis during submergence, followed by extreme water and salt conservation for at least 22 hours after the swim.