Sign Up

Already have an account?

Forgot your password?

Get back to the

Reset your password

Robert Downey Jr. Gained 20 Pounds of Muscle for Iron Man 2

1272919751_robert downey 290

Robert Downey Jr. packed on 20 pounds of muscle to reprise his role in Iron Man 2.

"When we did Iron Man 1, we had five months before the shoot to get ready, so we used more traditional, heavy-weight training," his trainer, Brad Bose, tells This time around, the actor, 45, had just wrapped Sherlock Holmes, and was down to 151 pounds when shooting on the action flick (out May 7) began.

PHOTOS: Summer movie romances

"After [the first routine], Robert felt kind of bored with it and wanted to something a little more exciting… so we decided to do what I call a Rocky IV meets high-tech training," says Bose, who bulked Downey Jr. up to 175 pounds over the first three to four weeks filming.

Examples: "Instead of doing regular bench presses, we used a bamboo bar… and we would hang plates on rubber bands off the bar… so it was like trying to bench press a snake!" Bose explains. "It bounced all over the place."

PHOTOS: Shirtless guys!

Downey Jr. also pushed "a custom-built wheelbarrow that we modified with 600 to 700 lb. weight stacks" around an obstacle course.

"We went out and bought truck tires, and we used sledgehammers — anywhere from, two 4-lb. sledgehammers in each hand, all the way up to a full 20-lb. sledgehammer — and we were just beating tires with it. We used fire hoses that we filled with sand and water… and we'd drag and whip them to build the shoulder muscles and pecs back up."

They also juggled "weighted Indian clubs," hulled around kettle bells and even used a war machine, which Boyes explains is "like a rope with handles on it with a pulley — you suspend yourself from it," says Bose.

"We tried to find the most unique, and yet funnily enough, inexpensive training stuff to use," he says. "You couldn't find more practical stuff to use."

VIDEO: How to get a six-pack

The two would meet around 9:30 in the morning and work out for an hour-and-a-half at least three days a week. Downey Jr. also trained in kung fu two to three days a week with Eric Oram.

For access to all our exclusive celebrity videos and interviews – Subscribe on YouTube!