You'll feel the burn — in your abs and shoulders — from this bodyweight exercise, which also adds a boost of cardio.
- Begin in an elbow plank position with your abs engaged.
- Draw your left knee into your chest. Then step your foot back to the elbow plank position. Now draw your right knee into your chest and then step it back to the elbow plank position.
- This counts as one rep. Start with 12 to 15 reps, and do at least two sets.