Actors Channing Tatum and Jenna Dewan went through grueling training to prepare for the teen dance drama Step Up, and they were left battered and bruised.

The film, which features Tatum as a bad boy who fills in as Dewan's dance partner, grossed a surprising $20.7 million at the US box office over the weekend.

He explains, "I did fall on my head once. Jenna bruised her rib doing one lift."

"We were practising it, and I bruised her rib a little bit. You're always sore and you have bruised knees."

Dewan, a real life dancer who has worked with Sean 'Diddy' Combs, Janet Jackson and Justin Timberlake, claims the tough conditions brought the cast together and they often socialised together.

She adds, "We had like our spots in Baltimore (Maryland) where all of us would get together and go eat and go dancing. We'd actually go dancing after we were dancing all day!"