Chaz Bono Cross-Trainer

8/28/2011 6:00 AM PDT

Chaz Bono -- Cross-Trainer

Chaz Bono toned up for his big debut on "Dancing With The Stars" by hitting the gym in West Hollywood Saturday.

TMZ broke the story ... Chaz will be a celebrity contestant on the show and will be paired with a female dancer ... a stroke of genius on the part of the producers.

Partially covered by a tank top and tattoos, Chaz kept it healthy with bottled water to beat the heat.