When you're working out, getting to the core of the matter doesn't always mean being static. Yes, holding an elbow plank will work your core, but to really fire it up, take those elbow planks for a walk. The challenge of moving your body forward and backward, as well as side to side, works your abs, back, and arms nicely. Plus it is more functional, meaning when you add motion to your planks, the movement pattern translates more closely to moves you do in your regular life. Strength training this way also helps prevent injuries. I learned this move at the Nike Women's Media Summit, and I really felt it in my abs. I may never do another sit-up again. Only kidding! But try it out and you'll see what I mean.

To see how to walk your plank, just read more.
First off, I know walking on your elbows doesn't sound all that comfy, so make sure you have some padding. If you have a yoga mat, just double it up at the front.

• Start in an elbow plank, with your elbows directly under your shoulders. Your palms should be flat on the ground and in line with your elbows. Pull your abs toward your spine and reach through your heels to activate the back of your legs.
• Walk about half an inch forward with your right arm. Your feet do not move. Walk the left arm forward so it is even with the right arm. Walk back a half inch with right elbow, and then your left.
• Now repeat starting with the left elbow, taking one step forward with each arm and one step back.
• Next you will step your right arm to the right about a half inch. Then bring your left arm a half inch to the right as well. Return to starting position, stepping first with the left arm and then with the right. Once again your feet should not move.
• Reverse directions and step the left elbow to the left, with the right arm following. Then return to back to center stepping first with the right arm and then with the left.
• Now add another two steps in each direction. Walk forward right, left, right, left and then backward right, left, right, left. Repeat starting forward with the left arm. Walk backward starting with the left.
• Walk to the right for four steps. Return to center and repeat walking to the left.
• Push back into a Downward Facing Dog and hold the pose for five breaths. Then repeat the series two more times.

Aside from working your core and your arms simultaneously, another reason to love this exercise is that it works in two planes, which will help increase your overall fitness level.