Greg Glassman, founder and CEO of CrossFit, believes his exercise program works for everyone. CrossFit workouts are the same for every person who walks into a gym. The only differences are the amount of weight used and the intensity. "Our understanding is that the needs of Olympic athletes and our grandparents differ by degree, not kind," Glassman told CNBC. "One needs functional competence to stay out of the nursing home. The other one wants functional dominance to win medals."

This approach has been a magnet for criticism. Some are skeptical of a single approach to training all clients. There are concerns that the competitive nature of the workouts might lead to injuries, and others call out the culture and label CrossFit a "cult." That'd be enough for most people to second guess themselves, but Glassman has never wavered. "I'm more comfortable arguing than I am being told how wonderful my program is," the 59-year-old founder said. "You're not going to do anything significant in this world without having people hating you for it." Glassman intended CrossFit to be a departure from what he didn't like in the "big box gyms."

The community allows me to lead. ... When they're done with me, they'll let me know. Greg Glassman CEO, CrossFit

He was working as a personal trainer at franchises like Gold's Gym when he began developing his program. Glassman's methods were visibly different than other trainers and were often met with a raised eyebrow. "It was always the odd thing in the corner going on with Glassman at the Gold's," he said. According to Glassman, the fitness industry "couldn't have been more wrong" before CrossFit.

Greg Glassman, Crossfit Founder & CEO, at the iConic:Seattle conference on April 5, 2016. David A. Grogan | CNBC

"I mean you sit on this thing, you put the pin in the hole, there's only one way you can move it, and that's not really what people need," he said.

"It was devoid of functional movement that is naturally occurring, these movements that are built into your DNA like standing up from a chair and picking something up off the ground," Glassman said. "Those are two essential movements. They're essential for your functional independence. They're essential to your health," he said.