The plank is one of the greatest exercises for working a whole bunch of different muscles at once (including those hard-to-reach lower abdominals) with no equipment other than a flat surface. And ...

Planks are a simple, equipment-free exercise that strengthen your core, improve posture, and protect your back ...

YOU PROBABLY THINK you know how to do a plank. The ab training staple is relatively simple, after all—boiled down to the basics, all you need to do is get down on the ground and hold in place.

Pilates pro Simone de la Rue demonstrates how to do a plank jack—aka the ultimate cardio and core-strengthening move—with proper form. A little known fact about planks: In addition to working nearly ...

Add Yahoo as a preferred source to see more of our stories on Google. YOU KNOW THE SAYING: Work smarter, not harder. You may have already incorporated that mentality into your training routine, ...