Plank Show Video Show All Exercises     Primary Muscle Group: Abdominals - transverse abdominis, rectus abdominis, and external and internal obliques Muscle Groups Worked in This Exercise: Abdominal muscles, lower back (erector spinae) and shoulders (deltoids), middle back (rhomboids) Preparation: Lie on your stomach on a mat with your legs together and the balls of your feet on the floor. Tighten your abdominal muscles. Breathing: Breath normally. Do not hold your breath Execution: Lift your upper body off the mat and then use your forearms to support your upper body. Position your elbows directly under your shoulders, with your hands clasped. Supporting your weight on your forearms and the balls of your feet, slowly lift your hips off the mat until your body is parallel to the floor. Hold the position for at least 15 seconds or as long as you can maintain good form and then slowly lower your hips back to the mat. Comments: Do not lift your hips too high. Keep your entire body parallel to the floor. Do not hunch your shoulders or arch your back. Do not bend your neck. Keep your head, neck and back in a straight line. Do not hold your breath. Here are a few suggested alternative exercises: Ab Crunch Ab Crunch Obliques Ball Crunch Traditional Double Crunch Dumbbell Side Bends Lateral Bend with Barbell