1/6Bill Diodato
The Right Way
"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."

Hold the "up" portion of a push-up—the plank is that simple. Nixing the "down" takes your chest and triceps out of the mix, leaving your abs to do the work.

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