- Start in a traditional plank, shoulders over hands and weight on just your toes.
- With your core engaged, bring your right knee forward under your chest, with the toes just off the ground. Return to your basic plank. Switch legs, bringing the left knee forward.
- Keep switching legs and begin to pick up the pace until it feels a little like running in place in a plank position.
- Continue "running" in your plank for 30 seconds, then rest for 30 seconds.
- Challenge: add a push-up after every two "climbs" (right and left).