ALTERNATING LIMB PLANK
Begin on all fours on your mat. Keeping a flat back and tight core lift one arm and the opposite leg up and reach in opposing directions, hold for three seconds and switch limbs.
* Keep hands directly under the shoulder joint.
* Lift opposing limbs at the same time.
* You can modify this exercise to make it easier by dropping to your hands and knees, keeping the one knee on the mat the whole time.