This exercise works your entire core, arms, wrists and shoulders. It is a challenging exercise as you alternate from side to side and that is why I love it.
Start by positioning yourself in a plank position. Then place your right hand in the middle of the mat and rotate your torso to the side, extending your left arm above your shoulder and look up at your left palm. Your body should be in a straight line from your head to your heels. Hold this position for a few seconds then return to start position and rotate to the other side. Do 2-3 sets of 8-12. If you find this exercise too hard just do what you can.