Up-Down Plank Begin in a full plank. Lower your right elbow to the mat and then your left, coming into an elbow plank. Put your right hand on the mat, and straighten your right elbow. Do the same on the left to return to a full plank. Do 10 reps starting with the right arm, the do 10 leading with the left arm. Your arms will burn after this exercise, but your abs are still working — they keep the torso stable while moving between elbow plank and full plank. Image Source: POPSUGAR Photography