The New Rules of Abs
Master these seven static floor exercises.
The basic plank—toes and forearms on the floor, shoulder blades pulled and down, butt down, body straight—is harder than you might realize. But once you can hold it for 60 to 90 seconds with ease, move on to a more challenging version of the classic. (The exercises are organized in ascending order of difficulty.) Do them in front of a mirror so that you can monitor your form, and be sure to break when it goes off.
Plank with Feet Elevated
Raising your feet increases the load in nearly any exercise, and planks are no exception. You can make this harder by placing your feet (or your forearms) on a Swiss ball.