Getting Technical


David Cornthwaite played soccer for Principia College. After graduation, he went on to coach Prinicpia High School’s soccer team. He ran to stay in shape, but constantly looked for new exercise programs.

In 2008, a friend of his suggested he check out It didn’t take long for Cornthwaite to realize that it was exactly the type of workout he had been looking for.

“When I started seeing awesome results, I immediately started implementing it into the coaching I was doing with my soccer teams on the high school level,” he said.

Cornthwaite got his Level 1 certificate in 2009 and coached individuals out of the high school’s weight room. Then, four years ago, JoAnna Dettmann, co-owner of CrossFit St. Louis, invited him to become head Coach. Although he enjoyed coaching soccer, Cornthwaite’s passion was rooted in CrossFit.

Dettmann said she hired Cornthwaite because of his passion. “Full-time CrossFit is all I do and it’s very satisfying,” said Cornthwaite. “I love passing on CrossFit to anybody and everybody.”

His love for CrossFit has infiltrated all aspects of his life. “I think my wife probably would have divorced me if she didn’t tell me one day, ‘Let’s not talk about this anymore,’” he said.

Cornthwaite’s knowledge was another aspect that told Dettmann he would be a good Coach at CrossFit St. Louis. “He’s incredibly knowledgeable about the sport and makes sure all our athletes are learning the proper movements,” she said. “Safety is one of his biggest concerns.”

Last Rep

In fact, Cornthwaite is a self-proclaimed “technician” as he loves teaching people how to move correctly.

He said his day is made when he has the chance to show members just how far they have progressed. “To be able to compliment somebody after a year and say, ‘You know how much progress you’ve made and how amazing this is? You couldn’t squat before,’” he said. “It’s a pretty awesome feeling that I get to experience almost every day.”

Dettmann appreciates Cornthwaite’s acute attention to members. “David has grown as a Coach in so many ways,” she said. “One of the biggest things I’ve noticed is his ability to learn something about almost all our members. He’s very personable.”

His advice to other Coaches is similar to his overall life strategy: help each member succeed and look at goals, emphasizing on life-long health and fitness.

And the truth is, he lives what he teaches members, staying active by going on hikes with his wife and son. “We’re in this for the long haul and to be healthy for the rest of our lives,” said Cornthwaite. “When my son grows up and throughout his whole life, I’m going to be able to be active with him, be a good example for him and be able to be right there with him.”

Kayla Boyd is an intern for Peake Media. She can be reached at