Challenge: Up-Down Plank
"After you've mastered the basic plank, you can move on to combination plank movements," Kenzie said. "This one is a core and arm burner. Be sure to switch which arm you lower first."
- Come into plank position with your arms and legs straight.
- Beginning with the right side first, lower your elbow to the floor where your hand was. Then lower your left elbow to the floor where your left hand was (now you are in elbow plank, with your forearms parallel).
- Come back into the starting plank position on your right hand and then on your left. This completes one rep.
- Kenzie said to start with three sets of 10 reps to "ensure your form is correct and to build strength." Then, work your way up in even numbers.