2 takes on 6-packs

OF COURSE it's not easy being a superhero. Rescuing babes, sidestepping bullets, you know . . . and then there's the mercilessly tight costume. No point flying onto the big screen with flabby abs. Enter L.A.'s high-profile personal trainers Brad Bose and Sebastien Lagree. Bose, with a background in physiology and a private gym in Santa Monica, helped Robert Downey Jr. put on 20 pounds of muscle in five months for the just released "Iron Man." Frenchman Lagree -- whose Pilates Plus franchise has a cult-like following among the tanned and toned -- worked with Ben Stiller for his role as an action hero in the upcoming summer spoof "Tropic Thunder." For mere mortals, both trainers agree that if you want to get buff for summer, better get on it ASAP. First, read on:

What was your client's goal for getting in shape to play a superhero?

Lagree: For this role, Ben wanted to get sculpted and toned. He wanted ripped abs too. We did a lot of interval training with cardio and Pilates. He did the recumbent bike for 10 or 15 minutes and then the machines for 10 or 15. He also runs on his own.

Bose: The people at Marvel didn't want Downey to look too bulky. He's a scientist, and so he's more brain than brawn. He came in 20 pounds underweight and trained five times a week for five months. He did yoga, kung fu and hour- or 90-minute sets with only 40 seconds' rest in between each exercise.

What is the biggest mistake men make when they train?

Lagree: They work the same muscles -- biceps, shoulders and chest -- and then they reach a plateau and get frustrated. Or even injured. Guys want to increase their upper body size but don't work out their lower body muscles. They forget their core, inner thighs, obliques and abductors.

Bose: The macho effect. Men walk into a gym, see other guys and pick up the heaviest weight they can manage. They also get confused about reps. You should lift a weight that you can only manage for exactly eight reps. Not nine.

Which area are men most concerned about improving?

Lagree: It's all about abs. My clients don't want to bulk up because they wear designer dress shirts. They need to fit into a slim-cut Dolce & Gabbana suit. The guys I work with know that smaller doesn't mean weaker.

Bose: Guys I see want really well-rounded shoulders, nice pecs and a strong chest. They want a flat stomach instead of six-pack abs.

How long will it take for a guy to get killer pecs?