Start in the plank position with both arms straight (starting push-up position). (1) Lower yourself to your right elbow while keeping your left arm straight. (2) Lower to your left elbow as well. (3) Straighten your right arm and then (4) your left. Repeat quickly as in walking your arms up and down. Reverse directions at the half way point.
10x Plank Walk Up = 10x Left Arm and 10x Right Arm, 20x Total