4x2 - The Biggest Loser

Bob and Kim prepare their teams for this week's challenge: racing up the stairs of a 10-story building. With immunity as the prize, both teams will have to do their best. Meanwhile, the secret black team, trained by Jillian Michaels, is finally revealed to the other contestants, who will join them in competing for the title of "The Biggest Loser" and $250,000.