An exhausted Maggie has played hard and is taking a breather in a cool, shady spot. Photo by Carol Ostrom

Dr. Kobi Johnson, executive administrator of Puget Sound Veterinary Referral Center in Tacoma, answers this week's questions about exercising your dog. (See part 1 on exercise.)

Question: What needs to be taken into account when trying to exercise my dog in hot or cold conditions? What are the signs of overheating, and if my dog has overheated, what do I do?

Answer: Be especially careful on hot days. Did you know Alaskan sled dogs have warm fur coats and retain so much heat that they perform best at 0 degrees Fahrenheit?

I use this example because dogs don't sweat like humans. They can't eliminate heat from their bodies efficiently. This is why dogs handle exercise in cold climates much more safely than even moderate heat.

Dogs cool themselves primarily by panting -- breathing in and out to move air over the moist surfaces of their tongue, oral cavity and airways. This is called evaporative cooling, and it works fairly well, but slowly.

Exercise produces heat, and when a dog can't eliminate that heat, their internal body temperature rises rapidly. The result is heat stroke, a dangerously high internal body temperature that damages organs and circulation. It is life threatening.

Although it can be treated with aggressive emergency care, the resources needed can devastate your pocket book, and a significant percentage of these dogs do not survive. It's especially difficult on owners, because this condition is preventable with diligent care and monitoring.

Heat stroke can occur on even mildly warm days. Direct sunlight with no available shade or shelter, high humidity and low airflow combined with heat, are climate conditions that contribute to your dog's risk of heat stroke.

ANY dog that exercises on a hot day -- even with frequent rest and water available -- can develop heat stroke, because their ability to dissipate heat simply becomes overwhelmed.

(Jack, right, takes a break on a summer day in his yard in Snohomish. Photo by Joan Deutsch)

Major individual risk factors for dogs include obesity, pre-existing heart or lung diseases, old age, conditions requiring the dog to be on medication, brachycephalic breeds (those with shortened nasal bones and compressed faces, such as English bulldogs) and thick hair coats.

The most common symptoms of heat stroke are weakness; collapse; severe panting or labored breathing; bright red gums; vomiting, seizures; coma. Without intervention, these signs can progress quickly to death.

What should you do immediately? The safest ways to cool your dog are to remove him from direct sunlight, cover him with wet, cool towels, or hose his body and feet with cool water.

The blood vessels of the feet cool by dilating. Applying cool compresses to the feet or soaking in cool water will also help dissipate heat.

Fanning cool air also can help. Understand, though, that these procedures should be performed immediately and only as initial treatment.

Your dog's best chances frequently depend on getting rapid emergency veterinary care. Veterinarians have the resources to safely support your dog's internal systems while attempting to minimize internal damage.

Question: My dog wants to run, run, run. I'm afraid he'll run until he collapses. What are the signs that my dog may be overexerting himself?

Answer: In general, I say let the dog run. The owner needs to be concerned about factors the dog can't control: is the location safe for off-leash running, is the area exposed to open, bright sun light, are there stimulating factors, such as other dogs playing, that may distract the dog and prevent it from recognizing its own fatigue?

The owner may need to force occasional rest for the dog to cool down, drink and allow the owner to assess if the dog has had enough.

With healthy dogs, overexercising and overheating generally go hand-in-hand. Signs of overexertion tend to be the same as heat-stroke symptoms, listed above.

Question: Is it appropriate for owners to run dogs next to them on bicycles?

Answer: I discourage this. Although many dogs can run faster than their human companions, the dog is likely to overexert quickly. The owner has less of an ability to appreciate the dog's level of fatigue while they are concentrating on riding, and the dog is behaviorally stimulated to run along, possibly from a feeling of being left behind, and is less likely to slow down or stop and rest.

I actually feel the same way about running with your dog, especially a small dog. The dog is stimulated to keep up and will ignore its own fatigue.

The safest is to stop and rest frequently, and preferably, allow your dog to exercise on its own to the limit it sets for itself.

Forced exercise will exacerbate any pre-existing medical condition and runs the risk of overheating or overexerting your dog to the point where joints, muscles, respiratory and heart function and even internal organs can be damaged.

Dr. Kobi Johnson

Johnson co-owns the Puget Sound Veterinary Referral Center, a 24-7 multi-specialty and critical-care center in Tacoma. Johnson originally is from Maryland and graduated from the Atlantic Veterinary College of the University of Prince Edward Island, Canada, in 1995. In addition to his emergency-care practice, Johnson has a passion for advanced diagnostic imaging and MRI, as well as performance sled-dog medicine. He has many years of experience as a volunteer veterinarian for the Iditarod Trail Sled Dog Race in Alaska, and most recently the Race to the Sky, in Montana. He enjoys boating and fishing with his two rescue dogs, Winnie and Doug.

Read our past Q&As:

Veterinary Q&A: A killer called bloat
Veterinary Q&A: Initial care for new puppies
Veterinary Q&A: Knee problems in dogs
Veterinary Q&A: Flea-control treatment
Veterinary Q&A: Bearded dragon lizards
Veterinary Q&A: Vaccinations for indoor cats
Veterinary Q&A: Lumps and bumps
Veterinary Q&A: More on aging dogs and arthritis
Veterinary Q&A: Puppy and geriatric exams
Veterinary QA: What dogs can safely chew
Veterinary QA: Why does it cost so much to clean a dog's teeth?
Veterinary QA follow-up: More on cleaning a dog's teeth
Veterinary QA: When to spay or neuter

Do you have a question about pet health? Ask now! We'll pose some of your questions to a local vet in an upcoming post.