Play fetch. Or any other game that'll get you and your pet dashing and panting. Play fetch with a ball or Frisbee—or if it's nighttime, play in a fenced-in yard with a white or light-up ball. Catch bubbles using a special bubble-blower toy made for dogs. Engage in some intense chasing, with a toy on a rope, for example. (Don't use branches or sticks, however, since they can hurt a dog's mouth.)
Go swimming. Some dogs are natural water breeds; others require training before diving in. Begin in shallow water: Keep your dog on a 15- to 20-foot leash, and wade in with him, encouraging him to play. Never force him to go in beyond his comfort zone—belly-deep is enough, especially at first. As the water becomes more familiar, toss a ball a couple feet away to encourage him to go a little deeper. Don't let your dog go into currents, and if you're in a lake, get him a well-fitted canine life vest. Swimming is often ideal for older dogs or those with joint and other physical problems.
Grab a bike. Biking is best for dogs that weigh at least 20 pounds. Invest in a product that attaches your dog's leash to your bicycle, which will keep him away from the wheels and prevent accidents caused by holding a leash in your hands. Bike at a trotting pace, and if your dog pauses, don't attempt to pull him along—get off the bike and walk alongside it.
No matter which exercise you choose, play it safe. Always bring water for yourself and your pet, along with some healthy snacks. (In addition to reenergizing your dog, these can be used to regain attention if he is distracted by something along the way.) Jog with only one dog at a time, though you may be able to walk with two. Watch out for signs of over-exertion and dehydration, especially in the heat, such as rapid breathing, heavy panting, salivation, fatigue, and staggering. Try to exercise in the coolest part of the day, or head to a shaded area. The human palm has the same sensitivity as a dog's paw, Becker says, so touch your palm to the ground. "If it's too hot for your hand, it's too hot for them to be walking," he says. "We have to be careful with all these activities. We wouldn't go out and run the New York City Marathon the day we decided to do it, but a dog would happily follow along until it collapses."