The captain's chair looks like a tall, seatless chair with arms and a back rest. You climb into it via pegs or small steps to do exercises to develop your ab muscles. The chair uses some of the same muscles you use in hanging leg raises, but supports your back so it's more manageable for most people.
The American Council on Exercise named the standard captain's chair crunch one of the most effective ab exercises for stimulating the rectus abdominis and obliques after performing a small study that pitted the move against 12 other popular ab moves.
Incorporate different variations of the captain's chair crunch into your core workout program that includes other quality moves, such as the bicycle crunch, stability ball crunch and reverse crunch.
1. Standard Crunch
HOW TO DO IT: Mount the captain's chair and press your lower back into the back rest and grip the hand holds with your hands; elbows and forearms prop on the arm rests. Allow your legs to dangle straight down.
Pull your knees up toward your chest in a controlled manner. Engage your abs as you lift the knees by pulling the belly button toward your spine. Slowly lower your legs to the starting position to complete one repetition. Work your way up to three sets of 10 repetitions each.
Make sure you lift your knees above your hips, or you'll de-emphasize your abs and work mostly the hip flexors. Brace yourself strongly through the shoulders and back. You don't want to relax the shoulders or you'll end up sagging uncomfortably.
2. Straight Leg Lift
HOW TO DO IT: Assume your position in the captain's chair with your low back in the back rest and your hands on the grips. Your legs extend straight down to the floor.
Seal your legs together and bend from the hips to raise your legs parallel to the floor. Move slowly and deliberately — avoid swinging so that momentum takes over. Return them to the starting position, again using control to avoid swinging. Work up to eight total repetitions.
Straight leg lifts are an advanced move. If you feel pain in your back, stop immediately as you may be causing injury to your spine.
3. Oblique-Focused Crunch
HOW TO DO IT: Get into the captain's chair. Press your back into the back rest and hold yourself strongly with the arm rests.
Pull your knees up, but angle them toward the right side of your chest. Lower the legs to dangling. Pull your knees up, angling to the left side of your chest. Lower to start to repeat one repetition. Work up to three sets of 10 reps.
4. Single Leg Lefts
HOW TO DO IT: Place yourself in the captain's chair, your legs hanging toward the floor. Keep your shoulders relaxed. Tighten your abs and pull the right knee in toward your chest; leave the other leg hanging.
Release and repeat with the left leg to complete one repetition. Perform three sets of 10 repetitions.