3. Plank up-Downs

Get in to that familiar plank position with your arms out straight and directly underneath your shoulders, squeezing your rear and pulling your abs tight in to your back. Then, beginning with one arm, lower it down in to the mat so that your forearm is taking your weight. Follow this with the other arm and then move back up in to the normal plank position. Repeating this is great for tightening your core.

Around-the-World Obliques
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