The growth of his business there are more than 30 members already suggests he is on to something.
Veterinarian Dale Smith began working with Schultz at the gym where Schultz previously was a trainer, Studio Cove, about a year ago and followed him to 212 Fitness.
An avid runner, Smith was skeptical when his wife suggested he join her, because he didn't want somebody a trainer telling him how to do his workouts.
He'd also heard of boot-camplike workouts in which the trainer degrades class members to get results.
"This is the opposite of that," Smith said. "He's just got this relentless, positive attitude that really encourages everybody in the class. He's never critical but pushes everyone to their limits."
Schultz earned a bachelor's degree in biology at the University of California at Davis before joining the Marines in 2005.
"I joined because I knew I would regret it if I didn't," he said. "You have one shot at providing a service to your country."
His second deployment, for much of 2007, had him in Iraq as a scout sniper and infantry team leader in charge of small groups of Marines away from base and in rural areas.
He left the Marines, moved to Utah to ski in 2009, met his wife and stayed.
Today, he sees some parallels between his Marine team leader experience and what is happening at 212 Fitness: In both cases, small clusters of people form communities in which each member has the others' backs. When one member misses class, the others notice.
"There is almost an unstated accountability in our classes," said Schultz. "If they are another face in the crowd, it's easier to quit."
Kiley Pitano, 41, said that community aspect of Schultz's class hooked her, as did his "fun" workouts using free weights, plywood boxes, punch bags, gymnast rings, stationary bikes and sledgehammers for whacking semi-truck tires.
There's not a single machine plugged into an electrical socket at 212 Fitness.
An occupational therapist in the newborn intensive-care unit at Primary Children's Medical Center, Pitano had always been an "intermittent exerciser" before joining Schultz's classes about a year ago.
In the past, she said, "I went to workouts wanting to ignore everyone.
Now, "they are counting on me being there. I look forward to seeing them every morning," said Pitano, who goes to the 5 a.m. classes weekdays and at varying times on Saturdays.
She has seen "huge, huge progress," said Pitano. "It's helped me feel more confident and live life on my terms rather than feeling trapped in my body. It makes me feel like I can tackle this day."
Fitness 212 is small, for now, and that's by design, Schultz said. It has just 1,500 square feet and, aside from two bathrooms, is just one big room in a strip mall. "It's about having controlled growth," Schultz said of his business.
But the maxim also applies to his training ethic. While all the workouts are designed to build core strength and lean muscle, he is big on safety so that a member's new strength is sustainable.
"I'm not about high-risk, high reward," he said.
His main goal is to help people be fit for everyday life, which in Utah often includes skiing, biking, climbing and running.
"People are realizing that their health is about more than running on a treadmill at a big box that charges $10 a month," said Schultz.
Anabel Greenlee, who is in Schultz's 6 a.m. class several times a week, said she appreciates his attention to safety and his ability to tailor the workouts.
"We cross-country ski, hike, snowshoe, but … I can't do everything a 30-year-old can do," said Greenlee, who is 69 and has arthritis in her knees.
"He's good about saying, 'Instead of jumping jacks, do toe raises. Instead of squat jumps, do this.' I'm able to keep up."
One of her motivations is to avoid what happened to her mother, who lived into her 90s, but died after falling on stairs because she lacked the strength to hold onto the railing.
Smith, 56, said that after a year of training with Schultz, he still has sore muscles at times, a sign that his fitness is still improving.
"Josiah," he said, "has gotten me in better shape than I've ever been in my life."
Help for veteran entrepreneurs
O The Veterans Administration has programs to encourage veterans to start businesses and gives vets preference for government contracts, although Josiah Schultz did not use those to start 212 Fitness.
Loans for veterans are available through the Small Business Administration's SBA's Patriot Express Pilot Loan Initiative, www.sba.gov/content/express-programs.
Hitting 212: A Company Statement
The name of the new fitness studio 212 Fitness comes from the boiling temperature of water: 212 degrees.
"At 211 degrees, water is hot. At 212 degrees it boils. … Just one degree is transformational. This is the foundation of everything we do at 212, because we believe that one extra degree of effort makes all the difference."