The Summer Olympics athletes that Dr. Michael A. Ball cares for will run three days in Georgia's July heat, jump over logs and ditches, sweat off as much as 10-15 liters of body fluid an hour and carry other athletes on their backs.

Of course, the triathlon equestrian event where Ball, a medicine resident in the Cornell University College of Veterinary Medicine, is assigned won't be a picnic for the human competitors. However, the Cornell veterinarian will be in Atlanta July 21-26 to look out for the horses' welfare. The equine EMT, as he describes himself, will monitor the jumps and aid the animals if they get into trouble. Stationed miles out in the field for the most grueling part of the three-day event -- the cross-country obstacle course -- Ball will radio for assistance, if necessary. Help will come from the Olympics' on-site horse hospital at the newly built Georgia International Horse Park in Conyers, Ga., some 30 minutes from Atlanta.

Combining a first day of dressage and third day of jumping with the cross-country day's road-and-track trotting, steeplechase and obstacle course, the equestrian triathlon usually is not one of the high-profile Summer Olympics events. But the horses' safety is paramount.

"Our main concern will be heat and dehydration," Ball said, noting that Olympics officials have, for the first time in the games' history, shortened parts of the equestrian event course for the steamy Georgia venue. In addition, the General Olympics Committee has given permission to further modify the events as necessary on the day of competition to allow for extremes in weather conditions. "There will be the standard 10-minute rest periods when we check the horse's body temperature, heart rate, respiratory rate and muscle fitness. If they are not recovering (during pit stops) they will not be allowed to go on."

Horses will chill out with specially built, outdoor air conditioners, Ball said, describing the "Cool Concepts" evaporative-cooling devices where huge fans blow mists of water droplets to lower ambient temperatures as much as 15 degrees Fahrenheit. The thirsty steeds will slurp water and electrolyte solution but never Coca-Cola, Ball noted, because that Atlanta-bottled, official Olympics beverage contains caffeine, which is one of the prohibited drugs in equine blood and urine tests.

"There will be more than enough veterinary checks and balances to assure that horses are not pushed beyond humane limits," said Ball, one of more than 40 veterinarians from around the world who will monitor the equestrian events. It was during pit stops for previous endurance events, such as the April 27 Rolex Kentucky Three-Day Event in Lexington and the Essex M&M Mars Event at the United States Equestrian Team Training Center, where Ball also worked, that researchers learned more about equine metabolism under stress. By weighing horses before, during and after endurance riding events, veterinary researchers found the athletic animals can lose as much as 30 pounds of sweat an hour.

The equestrian competition evolved from a military tradition and was one of the ancient Greek games, along with chariot racing, in 680 B.C. Today, equestrian competition is one of only two Olympic events in which women and men compete head-to-head. Women riders often do better in endurance equestrian competition, Ball observed. Equestrian teams from 16 nations are scheduled to compete.

When he heads south from Ithaca, Ball won't take his personal horse, a Canadian Thoroughbred he trained and adopted from the veterinary college's research program after she successfully recovered from a treatment for a fungal eye disease. His experience with horses predates his Cornell enrollment (B.S. in animal science, 1987; D.V.M., 1992) when he worked six years, exercising show jumpers and Thoroughbred racehorses, managed several show stables and worked extensively in horse transportation in Rhode Island, New Jersey, California and Florida. Ball "took a year off" before entering veterinary school to work with an international equine transport service, supervising the shipment of horses as they flew around the world.

After the Summer Olympics, it's back to graduate school for the horse doctor. Ball will study here with John F. Cummings, the professor of veterinary anatomy whose research focuses on a horse disease that parallels amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease. Cummings and his colleagues are trying to determine the role of vitamin E deficiency in equine motor neuron disease (EMND), which seems to strike horses that eat large amounts of dried hay, rather than fresh grass.

Ball realizes that his expertise gives him a coveted front row seat -- or at least a place to stand -- at the Olympic equestrian events, most of which are sold out.

"I can't even get a pass for my wife ( Christine S. Cable, D.V.M., a surgery resident in the college) to work as my assistant," he said.