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Thirsty? Try water. (9/16/98)

What is the best thirst quencher during outdoor activities in 90 degree heat, Gatorade® or water?

According to A. Donald Johnson, RN, PhD, associate professor at The University of Texas Health Science Center at San Antonio, just plain water could be the answer. Dr. Johnson, from the department of chronic nursing care, School of Nursing, has a Department of Defense grant to determine how best to alleviate a combat soldier's dehydration and electrolyte imbalance during training exercises, war and routine outdoor work activities. Working with Lt. Col. Joseph Schmelz, U.S. Air Force, nursing doctoral student Charlotte Richmond and a group of volunteers, Dr. Johnson is testing Gatorade® and water to find a solution to the dehydration problem.

Since conflicts and war often occur in hot climates and since military training exercises are usually held during the summer months, San Antonio in August and September provides an excellent climate to simulate military training exercises.

"Chemical warfare is a constant threat," Dr. Johnson said, "so our research subjects don the mission-oriented protective posture (MOPP), a heavy suit used for protection, and walk four miles drinking only water. Later, the volunteers walk another four miles and drink only Gatorade®. MOPP gear greatly intensifies the probability of dehydration and its subsequent problems."

Electrolyte imbalances and loss of fluids can lead to thermal injuries such as heat cramps, heat exhaustion, heatstroke and death, according to Dr. Johnson. "Since the government spends millions of dollars in lost productivity and in caring for these problems can seriously hinder the military's ability to accomplish goals," he continued.

"The aims of this study are to determine the differences, if any, in the changes in serum glucose, sodium, serum and urine osmolality and potassium after five hours in MOPP gear," Dr. Johnson explained. "Temperature, total body water, blood pressure, weight and pulse, both resting and active, are measured. Differences in male and female body fat are also taken into consideration.

"The problem is, thirst is an imperfect index in fluid balance because people may not feel thirsty," he added. "If it is extremely hot and body fluid isn't replaced throughout a prolonged exercise period, the consequences could be serious, even tragic.

"Even slight dehydration causes physiological consequences. For example, every liter of water lost will cause the heart rate to be elevated by about eight beats per minute, the cardiac output to decline by one liter per minute and the body core temperature to rise by 0.3 degrees Celsius," Dr. Johnson said.

"Although the final analyses aren't in yet, it appears there isnít much difference between Gatorade® and water in alleviating dehydration or in user preference," he stated. "This is an important finding for the nationís military, since enormous amounts of fluid are provided for our soldiers and airmen."

However, there is one consideration, according to Dr. Johnson. Gatorade® has about 50 calories in an 8 ounce bottle.

"Some people are watching their weight," he concludes with a smile.

Contact: Jan Elkins (210) 567-2570