A dog’s life used to be easier: Take a six-hour nap, terrify a squirrel, have a little can of something for dinner.

But these days, a dog needs a day planner, what with the yappy hours, the dog-park play dates and now — yes, it’s come to this — working out down at the dog gym.

Ruby was three minutes into her regimen Wednesday at Frolick Dogs Canine Sports Club in Alexandria, pumping her little beagle legs along the treadmill at 2.5 miles an hour, her nose in endless pursuit of the treat held just out of reach by her personal trainer, Kim Gilliam.

In a region filled with dog parks, doggy day care, dog walkers, dog-biscuit bakeries and rooftop dog-washing stations, the canine industrial complex has produced another indulgence: Fido fitness. Frolick bills itself as the Washington area’s first sports club for pets. For $50 a month, dogs get unlimited access to an air-conditioned 6,000-square-foot facility boasting two treadmills, balance balls (for that important core), cross-training and an agility course of hurdles, tunnels and balance beams.

Crazy? Like a foxhound. Frolick’s owners think they’ve hit on yet another way to add to the $56 billion Americans spent on their pets last year — an outlay that has almost doubled in the past decade and never stopped growing even during the economic downturn, according to the American Pet Products Association.

There are mobile dog spas and doggie daycares, now the newest thing to hit the canine market is a gym just for man’s best friend. A husband-and-wife team based in Alexandria, Va., opened the first canine sports club – complete with treadmills, box jumps and showers. (Whitney Leaming/The Washington Post)

“It’s grown even faster than I thought it would,” said Kevin Gilliam, a longtime dog trainer, of the business, which he recently opened with his wife, Kim, in an empty warehouse off Duke Street.

In their first five weeks, there have been sign-ups by dog owners who say summer dog runs are too hot (for dog and owner alike), who want their pooches to shed pounds and who are getting too old to keep up with their still-frisky pets. One customer had recent back surgery, so his Rhodesian Ridgeback now logs miles on the treadmill.

Some of the leggier breeds pant along the rubber belt just for the joy of running, the owners say. But others, like many a new gym member, need motivation. For Ruby, Kim offered the occasional morsel of kibble. It would drop, Ruby would stop to scarf it up and thus zoom backward, resuming her trot just a heel pad away from being shot backward like a little beagle bullet.

“Is that the cutest thing you’ve ever seen?” said a nearby client whose own dog was perched, quivering, atop a balance ball. A Portuguese Water Dog did reps on the balance beam. A chocolate Lab ran lap after lap behind the purple tennis ball her owner kicked across the floor.

The lab was Hazel, and her owner said she’s much happier getting her exercise inside during the summer.

“She’s very particular about the heat,” explained Justin Lang, 36, a work-at-home Alexandria writer.

Hazel gets outside about two hours a day, he said, but the dog gym gives her something extra: a greater variety of exercise, social time with other dogs and a solid workout. “In here, she’s good for an hour.”

The Gilliams know they have the perfect test market for their gym in famously dog-centric Alexandria, a place of dog happy hours, dog masseuses and monthly canine cruises on the Potomac. The city’s mayor is scheduled to be at the gym’s official grand opening Thursday.

“It it’s going to work anywhere, it’s going to work here,” said Kim, who has an MBA and 10 years in marketing and rattles off stats about pet spending and Alexandria residents’ disposable income with ease.

The pair is riding a cultural shift that has seen the nation’s 83 million dogs promoted from possessions to family members in recent decades. Kevin, who grew up with dogs in Alexandria in the days when giving them a little bacon grease for a shiny coat was the height of pet pampering, said the idea for the gym came from dog-training customers who told him that they were eager for yet more ways to lavish more time and money on their animals. Many of the dog owners are part of the region’s urban renaissance, former suburbanites who worry that their pets don’t get enough cardio in the city.

“They had a yard, and now they only have a postage stamp of grass in Old Town,” he said.

Industry observers think that the idea of dog gyms will be embraced all over in a country that gladly spends more than $300 million a year just on pet Halloween costumes.

Kit Yarrow, a consumer psychologist who has studied pet-spending patterns, had never heard of a dog gym before. She practically slapped her forehead.

“It’ll be huge!” predicted Yarrow, a professor emeritus at Golden Gate University in San Francisco. “Pets are humanized more than ever. Pet products are marketed more and more as if dogs are furry little babies.”

Owners are buying it, Yarrow said, because that’s just how Americans see their pets. More households don’t have children, she noted, and more people live alone. In a world that people see as increasingly rude, polarized and isolated, the ever-faithful dog is seen as a source of emotional support, her consumer surveys show.

“People are grateful for that, and that gratitude is translated into spending more money on them,” Yarrow said.

Even the Gilliams, as their four-footed clients burned calories behind them, wondered where the limits of pet spending could be found. Swimming pools for dogs? They have those. A hyperbaric chamber for dogs? There’s a local vet with one, Kevin said.

Kim told of an acquaintance who has been developing high-end, hyper-expensive prosthetic legs for dogs.

Kim, the business woman, asked, “Who would spend that much money?”

Kevin, the dog guy, answered, “I would.”