I never go to the gym, yet I stay in good enough shape not to get winded when I bypass escalators and elevators to sprint up long flights of steps in the New York City subway system. Interval training — short spurts of aerobic activity several times a day — is all the rage in workout circles. Well, it seems I was an interval-training pioneer.

Why is that? Because I have four large, athletic dogs, who serve as my personal fitness trainers in addition to my best friends. Together, we practice the dog-walk workout every single day of the year.

We’ve seen that walking the dog is not a chore but a fun bonding activity that deserves the handler’s full attention. We’ve also seen that dog walking after dark has its challenges. But dog walking as physical fitness routine? Well, why not?

Cardiologists say that walking is the heart-healthiest exercise there is. If you have a dog or three, then you know that walking must happen several times each day. There’s just no way around it. Dogs become your four-footed fitness gurus, and they offer this service for free as one of their many labors of unconditional love. What’s more motivating than, say, a German Shepherd standing over you as you wake up in the morning, demanding to be walked?

More is definitely more in the case of the dog-walk workout: The more you just do it, the more fit you become. You start jogging, then sprinting, then going longer distances. You look forward to raising your heart rate with your dog by your side.

Not long ago, I dated a man who was super athletic. He’d run the famed NYC marathon and was proud to have mastered many sports. After we took my strong-pulling dogs for a run along the parkway near my place, he groused the following couple of days about how sore he felt — apparently, my dogs had given him one hell of a core workout!

I photographed him as he gamely tried to walk my strongest puller, Magnus. After hearing his lament, it was interesting to review the images and see how his body tried to find equilibrium. Indeed, the pictures reveal just how much of a workout his core got that day as he twisted and turned to stay in step.

Well, I get that workout every single day. And being someone who loves nature and the outdoors, I’m repelled by the thought of working out inside a smelly, germy gym. Eww!

Since walking and running with my dogs is my main physical activity these days, I take it very seriously, starting with the gear. To support my “dogs,” I wear the most colorful Newton Running footwear I can find. It’s cold out there, so I make sure we stay comfortable with polar fleece: leggings for me, and on extremely cold mornings and late nights, a bodysuit for my short-coated dogs.

On snowy days when the sidewalks are encrusted with caustic ice-melting salt, the dogs wear Ruffwear’s rugged performance booties with Vibram-treaded soles. On not-too-cold days I slather on hand cream in lieu of gloves; when the temperature really dips, I wear gloves so my hands won’t freeze up. A bonus: The gloves help prevent wear and tear on my palms from the dogs’ leashes.

Prior to heading out, I make a point of stretching. I wasn’t always good about this, but observing how my dogs instinctively pause to assume the downward dog yoga pose right before we leave, I’ve been well trained to remember just how important it is to stretch. My dogs really are my fitness gurus!

Holding the leash is an art, at least if you want to prevent injury. I make a point of keeping my elbows bent; in case I get yanked when a squirrel passes, the sudden jolt won’t dislocate my arm from its socket.

Posture really does count, especially when you’re walking dogs. Again, to prevent arm dislocations, I keep my back as straight as I can, my shoulders rotated back, and chest out. When running with my four-footed fitness fiends, I opt for the grassy parkway near our place rather than the concrete sidewalks, so none of us overtaxes our feet.

I studied modern dance at college and later took classes at Martha Graham School of Contemporary Dance. If I’ve managed to keep something vaguely resembling a dancer’s physique in my mid-40s, I owe the achievement to my beloved dogs, who keep me on the straight and narrow. Thanks to my pack, I’m dedicated to a day-in-day-out fitness regimen, which is as good for me as it is for them.

Dogster readers, do you approach the dog walk as a workout? Have your dogs kept you out of the gym and in shape? Please share in the comments!