The plank engages the deepest abdominal layer, the transverse abdominus, and the obliques, which aren't targeted in standard ab exercises," says Cedric X. Bryant, chief science officer for the American Council of Exercise. "Plus, you firm your back, hips and shoulders." Master the move with our pro pointers.
The Right Way
Hold the "up" portion of a push-up—the plank is that simple. Nixing the "down" takes...
