A tempting slab of sidewalk for tomfoolery

A drunk man in his 30s barked like a dog and leaned over at the waist to flex his un-muscular frame as he strutted past an open-air storefront gym on his way to Wrigley Field to see a concert.

A dozen sweaty people struggling with kettlebells looked over.

Their instructor, unfazed, answered by clasping his hands and craning his corded neck into another classic muscleman pose.

And such is the witty repartee Sean Griffin exchanges with passersby of all stripes and alcohol contents who shuffle past his group training gym on their way to the ballpark or any number of nearby taverns. The barker this day was headed to a Phish concert.

Chicago Primal Gym, 3412 N. Sheffield, has floor-to-ceiling windows that fold open, offering fresh air and more.

“Guys always want to walk in off the street and do pull ups. Some women do too,” Griffin said. “I challenge them to do 10. And if their form is wrong I correct them and tell them to keep going.”

No one’s ever completed the challenge. Humbled and out of breath, most push on.

“It seems like some of the people might have been athletes in a former life and get drunk and try show off . . . or re-live athletic feats,” Griffin said.

“We’ll occasionally close our doors, but that’s pretty rare. It’s kind of part of the fun. We go with the flow of the neighborhood,” said Griffin, who does not take exercise too seriously. His website features a straight-faced man in a shark costume lifting a kettlebell.

On another occasion, Griffin said his class heard a disturbance and looked out to see a woman doing a downward dog yoga pose.

“This woman just started yelling out yoga moves and performing them on the sidewalk,” said Griffin, 30, a Wrigleyville native.

“There’s a good amount of heckling, which can either be funny or slightly obnoxious, but it’s usually in good spirit.”

Sometimes, though, things just get weird.

Griffin, who’s owned the business for three years, said three drunk guys and a female companion stood on the sidewalk outside his gym last November at 5:30 a.m. and aped the stretching maneuvers of his group. The front windows were closed, but the front door was not locked.

“One of them comes in and he’d taken his shirt off and had his shorts hiked way up and he started doing lunges. And then, his friend came in and dropped his pants,” Griffin recalled. “It was all fun until then, and then I was like ‘You guys gotta go.’”

“Another time a man who seemed intoxicated joined in a warm-up exercise and one of my longtime members threw an elbow at this guy because he was in the way and about to run into someone. So that was fun,” he said.

Most shenanigans take place on Fridays and Saturdays when the Cubs are in town.

“It’s always very interesting,” Griffin said with a chuckle.