Elbow plank [1] is already hard, but hold on to your leggings because it's about to get even harder. Grab a pair of hand towels (or paper plates on carpet) and try this sliding elbow plank.

• Begin in an elbow plank position with a small, folded towel under each elbow. Keep your elbows directly under your shoulders, your back flat (with a neutral spine), and your core tight!
• Slide your right elbow forward until your arm is nearly fully extended. With control, bring the right elbow back to center.
• Repeat on the left side. This completes one rep. Continue alternating for 30 seconds.
• If you need to modify, you can drop to your knees (while keeping your back straight and core tight); you'll still work the core and triceps!