On Tuesday night's episode of E!'s new reality TV series "Just Jillian," former "Biggest Loser" star and health and fitness guru Jillian Michaels can't hold back her competitive side- not even when her opponents are in their 70s. In a sneak peek for tonight's episode, Michaels agrees to play a game of pickleball against her partner Heidi Rhoades' elderly parents and refuses to throw the game just because of their old age.

"You're the most competitive person ever but remember it's supposed to be fun, it's for my parents," Rhoades tells Michaels in the couple's joint on-camera interview. "It's not for you to win."

"It would be a shattering brand crusher to lose to what'd you call them, septuagenarians? Yeah, no. Oh no," Michaels replies.

During the game, Michaels serves the first ball and Rhoades' father hits it back, then Michaels takes another hit, but Rhoades' mother said it was out of bounds. Michaels challenged Rhoades' mother's call.

"I don't even think the court's regulation to be honest," Michaels says in her on-camera interview in an attempt to explain her bad serve.

"It was the perfect serve, I'll have you know," Michaels tells Rhoades' elderly parents.

"It wasn't perfect, you didn't get in the square," Rhoades' mother replies.

Michaels pulls Rhoades aside and accuses her mother of cheating, and her father urges them to get back to the game. It's Rhoades' turn to serve, but the ball goes out of bounds again, much to Michaels' disappointment.

Rhoades' parents score another point during the next round, and Michaels pulls Rhoades aside again and asks her to step up her game, telling her to "focus," but Rhoades refuses.

"You're not even going to try? Then I don't want to play with you," Michaels tells her partner.

Watch the full sneak peek below and be sure to catch tonight's episode of "Just Jillian," airing at 10 p.m. on E!