What Is the Difference Between Raising Legs or Lifting Knees in a Captain's Chair Exercise?

The captain's chair offers an alternative to standard lying crunches, allowing you to work the abdominal muscles in a vertical body position. The technique is similar for the raising legs and lifting knees versions, with only the angle of your knees changing. However, this one adjustment affects the difficulty of the exercise, making the raising legs exercise an advanced variation of the lifting knees exercise.

  1. Technique

    • Mount the captain's chair with your back pressed against the support pad and your legs hanging directly below your torso. For the lifting knee version, bend your knees and pull them up and in toward your chest. For the raising legs version, lock your knees into a slight bend. Keeping your legs extended, lift them up and in toward your chest. For both exercises, when you reach the top of the motion, bend your waist, tilt your pelvis and pull your hips off the support pad to fully activate your abs. Slowly lower your legs all the way back down to the starting position.

    Muscles Worked

    • The raising leg or lifting knee exercise in a captain's chair works the same muscles. The hip flexors, or iliopsoas muscles, are the main movers during the first 90 degrees of the exercise -- until your thighs are parallel to the floor. From the 90-degree point, the abdominal muscles become the main movers as you bend your waist and tilt your pelvis upward. The rectus femoris, or quadriceps muscle, is also involved in pulling your thigh up toward your torso and is active during both versions of the captain's chair exercise.

      Although the hip flexors are the primary movers during the first portion of the movement, a study by the American Council on Exercise found the captain's chair exercises to be more effective at activating the abdominal muscles than the standard crunch.

    Difficulty Level

    • The raising legs version of the captain's chair exercise is more challenging than the lifting knees version. Extending your legs places more resistance farther away from the point of rotation, making the movement considerably more difficult. Start with the lifting knee version. Once you can complete 15 to 20 repetitions, advance to the raising leg version.

    Precautions

    • Both versions of the captain's chair exercise are advanced abdominal movements compared to the standard crunch. Your abdominal muscles isometrically contract -- activate with no significant change in length -- throughout the captain's chair exercise because they work to stabilize your body in the suspended position. Even during the first portion of the movement when the hip flexors are the main movers, the abdominal muscles are isometrically contracting. Strengthen your core muscles with basic crunches before advancing to the captain's chair exercises.

      The captain's chair exercises place a higher load on the lower back than the standard crunch. They can be contraindicated -- especially the extended leg version -- if you have any low back problems.