Side Plank Reach Through (Right Side) Start in side elbow plank on your right side with your feet stacked. Raise your left arm in the air. Lower your left arm in front of your chest and reach it underneath your rib cage through the space behind your right arm. Reach your arm back up into the air to complete the rep. Keep going for 40 seconds, followed by a 10-second rest. Image Source: POPSUGAR Studios