HOW: Start in a push up position with toes pushing into the ground and your shoulders, hips, and knees in a straight line. Have a slider of some sort underneath one hand. As you go down in the push up, slide the slider out in a lateral direction, then back up to the starting position as you push up. Perform this sliding out to the side, diagonally, and forwards for the prescribed amount of reps.
FEEL: You should feel you chest and core muscles working.
COMPENSATION: Keep you core engaged to make sure you are dropping your hips or raising your hips during the push up.
