“THE MUCH-COVETED INGUINAL CREASE”: Building a Bigger Action Hero.

Since 5 percent body fat is nobody’s natural condition, fitness plans are geared to peak on the days of the sex scenes or shirtless moments. To prep for these days, trainers will dehydrate a client like a boxing manager sweats a fighter down to weight. They often switch him to a low- or no-sodium diet three or four days in advance, fade out the carbohydrates, brew up diuretics like herbal teas, and then push cardio to sweat out water – all to accentuate muscle definition for the key scenes.

The last-minute pump comes right before the cameras roll. Philip Winchester, the hero of Cinemax’s action series Strike Back, recalls seeing the technique for the first time on the set of Snatch: “Hundreds of extras were standing around,” he recalls, “and Brad Pitt would drop down and do 25 push-ups before each scene. I thought, ‘Why is he showing off?’ ” Then Winchester figured it out. “I realized he was just jacking himself up: getting blood flowing to the muscles. I’d always wondered, ‘How do actors look so jacked all the time?’ Well, they don’t. Now we ask: Is it a push-up scene? When I shot that Strike Back poster, I was doing push-ups like a madman, saying, ‘Take the picture now! Take it now!'”