This exercise is fantastic for the core. Strengthening your core improves your posture, back pain and althletic performance preventing sports injuries.
Start by getting on your hands and knees on your mat. Make sure your hands are parallel underneath your shoulders and your abs are held in tight. Begin by lifting your right leg holding it straight at hip level, then lift your left arm holding it at shoulder level. Hold this position for 5-10 breaths making sure to hold your abs in tight. Return to start position and do the other side. Alternate from side to side. Do 2-3 sets 16-20 reps.