Encontré esto acerca de la camisa de fuerza o camisa de levantador:
"A super-shirt, mostly. In 1983, a college student and powerlifter named John Inzer started making shirts that supported benchers' shoulders and deltoids. Word spread that the bench shirt not only prevented injuries but actually helped bounce the weight off your chest. The terminology on Inzer's Web site reeks of pseudoscience—the top-of-the-line Inzer Phenom shirt "features the EVS (Escape Velocity System) built inside"—but the shirt's effect is undeniable. As the record for the shirted bench press shot up to 965 pounds, the unshirted or "raw" mark has stayed at an earthly 713 pounds. (Scot Mendelson has that record.) Nowadays, every top bench-presser uses the shirt for safety and power. "The whole raw thing, you're just asking for trouble if you're going to be dealing with any kind of weight," says Ryan Kennelly. "If you rip your pec, you rip your rotator cuff, you're out of there. Thank God for bench shirts."
The bench shirt—which comes in denim or polyester—has arms that jut out zombielike, perpendicular to the chest. The position is so awkward and the fit so tight that lifters typically need help swaddling themselves. As the bar starts to press the weightlifter's arms down, a percentage of the load goes to deforming the shirt. High-end shirts are so taut that for the bar to even reach a bencher's chest, the fabric has to be compressed with incredible force. (At one meet, Rychlak had to abandon an 890-pound lift because it wasn't heavy enough to force the weight down to his pecs.) When the bencher starts to push the bar back up, the shirt acts like a spring. As the material snaps back to its original, zombie-arm orientation, the lifter's elbows get a bit of extra help moving the weight back into the air.
Inzer says the bench shirt "brings out the deeper strength of a lifter." Powerlifting traditionalists and scientists think the opposite. Indiana University biomechanics professor Jesus Dapena says the shirt helps lifters hoist more weight by using their arm bones—not their muscles—as levers. "I would consider it cheating, it's helping you mechanically. You might as well have a pulley," he says. Even so, all the top lifters trot out the same line: "The shirt alone isn't going to lift that weight." And don't think wearing a bench shirt makes 1,000 pounds feel like nothing. Mendelson says that when he's pressing 1,000, "I can feel my bones flexing." The first time Kennelly held a half-ton he heard a humming noise and had blurred vision. "Now my central nervous system has adapted to it. I'm used to it," he says.
While the bench shirt has been around for two decades, the last couple of years have seen marked improvements in shirt design and technology and an increased focus on shirt-based training methods. Because bench shirts severely restrict movement, lifters must practice and memorize an incredibly precise sequence of steps to bring the weight from the chest to lockout. The bench press has now "become more a finesse and technique sport than a brute strength sport," says bench-shirt guru Bill Crawford, who leads the Metal Militia bench-press team. Rychlak, for one, could "probably put about 40-45 pounds on his bench by changing his body position and his feet."
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