Bob Harper's Recovery Means Walking Dog Is the New CrossFit

"The Biggest Loser" host Bob Harper's looking good following his major heart attack, and says he's taking steps toward recovery ... small ones with his dog.

The fitness guru's been posting pics letting fans know he's getting better, but says the only exercise he's allowed to do right now is walk Karl around the city and in the park.

We broke the story ... Bob suffered the heart attack 2 weeks ago and was unconscious for 2 days and hospitalized for 8.

Normally, he'd be competing in the CrossFit Open this time of year. Strolling with Karl's gonna have to suffice for now.