Lie face down on your stomach with your arms and legs extended and spread slightly wider than shoulder-width apart. Keep your neck relaxed and in line with your spine.
Keeping your arms and legs straight (but not locked) and torso stationary, simultaneously lift your arms and legs up toward the ceiling to form a shallow "U" shape with your body. Your back should be arched with your arms and legs lifted several inches off the floor. Avoid tilting your head back and keep your neck aligned with your spine.
Hold for two to five seconds, bracing your core and trying to stabilize your body as much as possible.
Slowly lower back down to the starting position.
This completes one rep. Complete as many reps as you can with proper form in 20 seconds.