Behind the scenes with all-athlete 'DWTS' cast

The all-star athletes in the cast of "Dancing with the Stars" have trained long and hard for their first ballroom performance, and "GMA" got a behind-the-scenes look at some of their preparation before they step into the ballroom tonight. Olympic luger Chris Mazder and his pro partner Witney Carson are dancing the salsa, while Sharna Burgess is working with former Washington Redskins player Josh Norman on the cha cha cha, finessing his football footwork. "[In] my sport I have spikes taped on my hand and I'm paddling into the ice so naturally my hand makes a claw-like structure," Mazder said. "And in dance, this looks terrible when it's stiff and off to the side," he said. "Unless we're doing a Gaga structure, then maybe," his partner, Carson, said joking of Lady Gaga's signature monster-dance move. Mirai Nagasu is hot off her historic figure-skating performance when she became the first American woman to land a triple axel in an Olympic Winter Games, and she's going to make a...