We all know that the plank is the perfect core exercise. We also know that we need to switch up our fitness routines to prevent the plateau and boredom. Here's one of our favorite variations on the traditional exercise that has you moving between the basic plank and an elbow plank. Add this move into your fitness routine to tone your arms and work your center. Just make sure to do this on a padded surface so you don't bang up your elbows.