may be happily married to Andy Roddick
but, according to the model
, it's probably best for the two to keep their professional lives separate.
"He tried to give me a lesson once, and I ended up hitting all the tennis balls over the fence and smashing my racket because I was so frustrated," Decker, 24, tells Women's Health
in its May issue.
"I told him, 'You don't teach me how to play tennis and I won't teach you how to model in a bathing suit.' "
"And," she continues, "so far it's worked."
Being married to the tennis star, 29, has helped Decker, who stars in the action flick Battleship
, gain a "new appreciation" for her body, she says.
"[Andy's] taught me that it's not how thin you are that matters," she says. "It's how your body performs – how it endures wear and tear."
Exercise, it turns out, is something that bonds the couple.
"One day when we were in London, Andy took me to a track behind a high school," she recalls. "We did a kind of hopscotch down the track – more drills over hurdles – and then shuttle runs."
For her role in Battleship
, which also stars Rihanna
, Decker says director Peter Berg told her she needed to bulk up.
"He took me to a boxing gym in Santa Monica," she says. "After six or seven minutes of sparring, I was completely winded. But I was also exhilarated because it was a new workout that I had never before experienced."