Doctors in Maryland issued a new hot weather warning to jogging fanatics yesterday: run until you drop from exhaustion if you must, but spare your dog.

Dogs may push themselves beyond their physical limits in an effort to keep up with a beloved owner on a hot day, warned Dr. Robert H. Batchelor, president of the Maryland Veterinary Medical Association.

And if this should happen, he said, pick up your dog and run - do not walk - to the nearest bathtub.

Dogs do not perspire as humans do, Batchelor explained, but lose heat mainly by panting. Panting works in two ways: blood is cooled by the air as it passes over surface vessels on the tongue, and body heat is lost in air exhaled from the lungs.

Panting is less efficient than losing heat through the skin, so a dog overheats more easily than a human, he said. Nevertheless, a dog may be so eager to keep pace that it may continue to run, raising its normal temperature of 101.5 degrees to dangerous heights: 106 or above.

Batchelor and other veterinarians said they see many more cases of heatstroke in dogs left in closed, parked cars than in jogging dogs. But in either case, a dog can die within a few minutes unless its temperature is lowered.

In ways not well understood, heatstroke causes a breakdown in an animal's normal process of heat loss, said Dr. Robert Mueller, a Bethesda veterinarian who treated several cases last summer at the University of Georgia School of Veterinary Medicine. There may be few warning signs - the dog will continue to pant, and it may or may not slow down or appear weak. Then it will suddenly collapse.

If this happens, Mueller said, the owner should take its temperature and, if it is over 103, put the dog in a cold bath until the temperature falls to that level. When the temperature drops to 103, he should remove the dog from the bath and take it to a veterinarian, where it may be hospitalized overnight to watch for complications, including abnormal blood-clotting.

A dog is safer jogging in the morning or at night than during the day when temperatures and humidity are higher, said Dr. R. C. Mackey, Mueller's partner in Bethesda. "It wouldn't be so bad if the dog would jog the same distance as the person, but the dog runs back and forth and all over. He runs at least four miles to your two," he said. A dog running with a cyclist is in danger for the same reason.

Mackey said dogs facing the greatest risk for heatstroke are large breeds like the St. Bernard, and the "brachiocephalic breeds": boxers, bulldogs and their relatives, whose flattened noses make breathing more difficult.

Batchelor said jogging is good for dogs, provided their owners are careful. "Just like humans, if they sit around the house all day, they lose muscle tone and become obese," he said. CAPTION: Illustration, no caption, By William Coulter for The Washington Post