The Biggest Loser The Biggest Loser

Tennis pro Anna Kournikova is heading to The Biggest Loser, a rep for the show tells exclusively.

Catch up on The Biggest Loser with our recaps

On Tuesday's episode, the remaining 15 contestants must compete in a tennis-workout challenge led by the 29-year-old Kournikova. The task quickly becomes a battle of the sexes.

Biggest Loser's Alison Sweeney: "We have a cast of a thousand this season"

This isn't the first time a major athlete has pitched in on the weight-loss reality series. Arizona Cardinals quarterback Kurt Warner appeared on Season 7, Olympians Jeret Peterson and Julia Mancuso and Dallas Cowboys quarterback Tony Romo were on Season 9.