Robert Kardashian Dancing With The Stars Hollywood DWTS Cheryl Burke Chaz Bono Dancing With The Stars Hollywood Sonny Bono Cher Lacey Schwimmer

Let's hope the Season 13 cast for Dancing With The Stars were prepared for all the hard work they signed up for!

Rob Kardashian and dancing pro Cheryl Burke left the rehearsal studio looking totally wiped out. Watch out, Rob ... Ms. Burke doesn't mess around, but her incredible work on the dance floor proves she's in it to win it. Let's hope Cheryl can convince Kim's younger brother to go shirtless for one of the numbers.

Chaz Bono and his partner Lacey Schwimmer also got their dancing groove on in the studio ... in preparation for the show's premiere on September 19.

See all of the couples leaving a hard day of practice in the gallery below.