The abdominal burn sneaks up on you while doing this move. You'll likely feel it in your shoulders, too.
- Begin in an elbow plank position with the abs engaged.
- Draw the left knee into the chest. Then step the foot back to the elbow plank position. Now draw the right knee into the chest and then step it back to the elbow plank position.
- This counts as one rep.
- Continue alternating sides and complete as many reps as you can in a minute.