Lay down on your back on a flat bench with your legs hanging off one end.

Extend your arms out above your head, and straighten your legs. You should be laying completely flat. This is the start of the exercise.

In one motion, while keeping your hands and feet together, raise your legs and bring your arms forward as if you were trying to touch them together.

Lower back to the starting position. Repeat for desired reps.

Jackknife Tips:

This is a very challenging exercise.The slower you do it the harder it is, and the more benefit you will get from it.

Your legs should be approximately 35-45 degrees from the floor. Yourarms should be extended and parallel to your legs at the top of the movement.