- 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. This counts as one rep.
- Keep switching legs and begin to pick up the pace until it feels a little like running in place in a plank position.
- Complete 15 reps.
- If this is too easy, place two 10-pound dumbbells under your feet and perform the mountain climbers.
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