This exercise is a great one to strengthen your core and work the entire upper body as well. It's a variation on the normal push up, which of course is one of my favorite things ever. A GREAT way to sculpt those arms, and increase your upper body strength. Begin in the start of a push up, an extended plank. Hold this position for 10 seconds. Slowly release down into a push up and back up to your starting position. Hold again for 10 seconds and repeat. Do this 15 times. Really focus on keeping your abs tight, glutes tight, and your body in line.