Growing up in Ithaca, New York, I lived with as many as three Australian Shepherds at a time. My mother trains the breed for competition in a sprint-speed sport known as dog agility, so it was a common weekend activity for my family to head out to some remote field to exercise the pack. The dogs, which are known for their ferocious stamina, would spend hours chasing whatever toy projectile we could throw furthest.

Many serious trainers like my mother take dog ownership into the athletic realm, competing in activities as diverse as sheep herding and dock diving. But even for people who are just looking to get into shape, the idea of exercising alongside a dog can be appealing. The internet is replete with health guides, lifestyle columns, and expert advice blogs trumpeting the benefits of dog ownership for health. As these sources often point out, dogs are great for getting you out the door. They’ll never judge you, and the amount of physical activity they need to stay trim and cardiovascularly strong is around the same for humans. Getting one seems like a fitness win-win.

Dogs are thought to have been fully domesticated tens of thousands of years ago, so the case could be made that humans and dogs have been working (and working out) together for millennia. Nonetheless, that doesn’t mean those wind sprints in the park after work are always a boon for dogs, even if they’re great for dog owners. Many vets caution that certain dogs don’t have the physique or the drive to endure a serious workout, and owners’ own fitness obsessions are wearing some dogs out.

Since jogging is so popular, many dog-exercise enthusiasts encourage bringing a dog along on runs. “When I’m home, I take my pack out for a run every morning in the canyon,” writes Cesar Millan, the celebrity canine behaviorist and star of Hulu’s Dog Nation, in a blog post about how dogs can be the secret to weight loss. “Argos, the three-year-old Greyhound, and Junior, the Pit Bull, require more than just an hour run, so I usually take them out for a game of fetch or hill climbing before dinner.”

The thing is, not all dogs are born runners. And just like humans, even those that are naturally athletic still need to build up their endurance. Particularly in urban areas, where open space is scarce, dogs can face a number of health risks when their owners push them through strenuous workouts, vets warn. “I think running with a dog is a wonderful thing, but it has to be done with just as much care as the person who is running takes,” says Richard Goldstein, the Chief Medical Officer of the Animal Medical Center in New York, a veterinary hospital. “The things we encounter are people running with the wrong breed of dogs, forcing dogs to run, and then just doing too much.”

As far as selecting the right breed, one of the most common recommendations from veterinarians is to avoid short-nosed, or brachycephalic, dogs. Even though some of these breeds, such as boxers, routinely show up on online lists of the best dogs for runners, their physiology makes running alongside humans more dangerous. “All of the brachycephalic breeds have very short noses, so all of their respiratory tract is in a very short space,” says Pamela Schwartz, a staff doctor at the Animal Medical Center. “Those breeds are at a very high likelihood of overheating—sometimes they’ll just run and play and not stop until they go into heat stroke.”

Heat is a big issue for all dogs, in fact, especially in neighborhoods with limited parks and green space. Not only can dogs overheat, says Joseph Kinnarney, the former president of the American Veterinary Medical Association, they can burn their paws.

“The only way dogs can dissipate heat is through panting, and that requires being able to lose water, so they get dehydrated very quickly,” says Goldstein. “You see runners with little bottles for themselves and nothing for their dog. They’re going to need water more than you do, so if you think you need water, they’re going to need double that amount.”

Most veterinarians say it’s important to hold off on any serious jogging with a dog—any “running other than puppy play,” in Schwartz’s words—until it’s fully grown, to avoid developmental issues. Unfortunately, how the demands of exercising with humans affect household dogs isn’t a question that has been thoroughly examined in the veterinary literature, so the impacts at any stage of life aren’t clear. The studies that do exist mainly focus on sled dogs or other working breeds that are more consistently active. And even the sturdiest hunting and herding dogs that have been bred for endurance and athleticism can have a condition that leaves them more prone to injury.

“Any breed, any dog can be predisposed to an orthopedic disease,” Schwartz says. “And if they are, the last thing you want is the dog running for extended periods of time in a way that could exacerbate this underlying condition that people may not know is there.”

Ironically, dogs might be so well adapted to the human environment that it’s easy to overlook the stress some face as pets. Given the resiliency certain breeds have shown in combat, emotional therapy, search and rescue, and other challenging settings, the expectation that they’d handle routine human exercise easily is understandable. And it might seem harmless to push especially active breeds beyond what their owners do themselves, for example by having them run alongside a bicycle. Some can handle this, but apparently not all.

In some ways, good intentions can be as much of a threat to the health of a dog as neglect. Dedicated owners might view regular exercise as more responsible than an occasional walk around the block. In general, many vets would agree. But as the human-canine relationship continues to develop, our understanding of dogs’ capabilities and limitations should improve, too. This might not inspire everybody to raise multiple energy-crazed competition dogs the way my family did, but it could definitely save some dogs from those sad summer paw burns.