Hit the Floor and Give Me a Dozen...Pillar Bridges

The regimen is called "core strength," and it's all the rage in fitness. Elite athletes from marathon runners to baseball pitchers are adopting core-strength workouts—that is, bolstering the muscles encasing their torsos from shoulder to thigh—in pursuit of improved performance and fewer injuries. Fitness trainers are preaching it to the masses. Books like "Core Performance," by NFL Players Association chief fitness trainer Mark Verstegen, hawk its benefits.