Here’s a video to spice up your normal ab routine. Add a little knee to elbow action to work on those obliques, abs, and shoulders.
Option 1: Bring your right knee forward towards your elbow and then return to plank position. Then repeat on your left side.
Option 2: Bring your right knee underneath your body and try to touch the opposite elbow. Then repeat on your left side.
Try these in a normal straight plank or your elbows bent in half plank. Do 3 sets of 20 (10 on each side).