(CNN) -- Kevin James trained for 14 months to play a biology teacher who moonlights as a mixed martial arts fighter to raise money for his school in "Here Comes the Boom."
James said training included working out three times a day, drinking greens, running and sparring. Yet, he was moving pretty slowly when he dropped by CNN last week.
"I threw my back out ... getting into a town car. That'll show you the kind of shape I'm in now. How far I've let myself go," the self-deprecating comic said.
James co-wrote and co-produced the action comedy, which hits theaters on Friday. It's already garnering positive feedback.
Among his favorite early viewer reactions: "God forgive me, I think I honestly liked this Kevin James movie."
Some people have the idea that "Here Comes the Boom" is "just going to be Paul Blart falling around a ring, being the fat guy, tripping over his own feet," James said. "But the UFC gave us their blessing to make this movie. ... I had to promise them I'm going to make this thing as realistic as possible and it's going to be something that they haven't seen in me before."
As several MMA sites have reported, this is the first film that's actually been allowed to use the UFC brand name.
So far it seems MMA fans like the way the sport is represented. Fight Network's Sarah Davis wrote, "I can appreciate all the cameos made by UFC personalities and fighters, whether they play themselves or not and there are a lot of fight scenes with superman punches, Kimura locks and body shots."
Since "The King of Queens," James has made a name for himself in the PG arena, headlining family films like "Paul Blart: Mall Cop" and "Zookeeper." And then there are his PG-13 endeavors, which include ensemble comedies like "Hitch," "I Now Pronounce You Chuck & Larry" and "Grown Ups."
Despite some critical reviews, James' flicks have consistently performed well at the box office.
As Entertainment Weekly reported after "Zookeeper's" 2011 release, 41% of moviegoers listed "actor in a leading role" as their reason for seeing the flick about talking animals.
James said he doesn't feel the need to defend his recent films, and he won't apologize for playing "the goofy guy falling down."
"I love doing it," he said. "It cracks me up sometimes what people will say about 'Paul Blart,' " the 2009 flick he co-wrote and starred in as a Segway-riding security guard at a New Jersey mall. "This is for families and for kids."
"Here Comes the Boom" is a very different kind of physical comedy, full of knockouts and arm bars.
Everything that happens in the film is something that has happened during a real MMA fight, James said, noting, "There was a ring that broke. A guy got thrown through the ring. There was a rain fight. These are all from real life."
James, who was a wrestler and a football player once upon a time, has been a fan of the UFC since watching the first fight in 1993. He said it was his "love of trying to be physical and trying to portray what these guys go through" that led him to the project.
As for the other half of the story: "I also have teachers that I remember from when I was going to school that have inspired me," he said. "I've also had really crappy teachers, unfortunately, where they don't really care that much and you think it's a great time then because you're in class ... but literally there is nothing for you later on down the road. I kind of just wanted to tie these two worlds together."
"It's tough," he added, "because you're trying to blend a big comedy with inspiration, with heart and realistic fighting. ... There are a lot of ingredients in this one."
James hopes audiences will enjoy the idea of a "common, everyday guy" fighting in the Octagon for a good cause.
"You can watch 'James Bond' and enjoy it because it's something that you would never do," he said. "I could never be James Bond. And then there are movies where you watch because you're seeing yourself through the eyes of the character. And I think I'm the latter."
Part of James' appeal as the everyman is his size, which is occasionally written into his story lines, as fans of "The King of Queens" already know.
While he said he doesn't mind the jokes, his mother is not a fan.
"If I do a movie where I have to have (a son) and it's a chubby kid, my mother is always like, 'You were never like that.' She gets so upset about it," he said.
It's his own kids, who are 7, 5 and 17 months, who have greatly influenced his professional decisions.
"I want to do movies that I'm proud of where my kids, at some point, can see and I can feel comfortable sitting there watching it with them," he said. "And just that move people. That make people feel a little bit better about themselves when they leave the theater."
James will next appear in "Little Boy" and "Grown Ups 2," which is due out in July 2013. He's also gearing up to star alongside Kevin Hart in "Valet Guys," the comedy he co-wrote about two valet parking attendants who witness a murder.