The slingshot move of a pro pitcher's shoulder is the fastest recorded action in sports. A pitch's power, however, is generated by his entire body. For a right-handed pitcher, the chain of kinetic energy starts as soon as he lifts his left leg and faces third base. The energy of that foot landing transfers into the rotation of the trunk and then finally unleashes in the arm whipping around at the elbow. Glenn Fleisig, the research director of the American Sports Medicine Institute, has found that the hardest throwers rotate their pelvis toward home plate and follow with their trunk less than a tenth of a second later, snapping their bodies like a whip.