Begin in a traditional plank position with both of your hands on the floor and your elbows and wrists in straight lines. Resting on the balls of your feet, brace your abdominals to maintain a neutral spine.
On an inhale, brace your abs, elevate your hips, and lift your left hand up off the ground reaching toward your right foot. It's OK if your hand doesn't touch your foot.
On an exhale, lower back to the starting position. This counts as one rep. Repeat on the right side and continue to alternate between the right and left sides.
Repeat for a total of 50 seconds, then take 10 seconds of rest.