Plank pose variation builds abs, upper body: Good form
Strengthen your core and upper body with this variation of a straight-arm plank. Be sure to keep both shoulders and hips level to the floor in order to make it as effective as possible.
Kneel on a mat and place your hands directly below your shoulders with your fingers pointing forward. Straighten your legs behind you with your feet 8 to 10 inches apart from each other. Balance on your hands and toes, forming a straight line between your shoulders and your ankles. Contract your abdominals to prevent your back from overarching.
Without changing the position of your legs, push out slowly through your heels and tighten your front thigh muscles. Shift your weight over your left hand and slowly raise your right arm next to your torso. Pause for two breaths, then switch arms, raising your left arm next to your torso. Repeat two times on each side, then release by bending your knees to the floor.