Although many people might not have heard of it, the Jackknife is one of a number of abdominal workouts that make use of the increasingly popular inflatable fitness ball or yoga ball. Somewhat more challenging than other abdominal workouts in some respects, the Jackknife is said to help participants target their central abdominal muscles in particular.
To perform a set of Jackknife abdominal workouts, you would begin with your body in a position that quite clearly resembles a push-up position. Yet, rather than resting both your palms and your legs on the floor, you will put your palms on the floor and put your shins, not your toes, on top of the inflatable fitness ball. After getting into this position, you will raise your bottom up into the air, bending your body at the hips. This also requires that you roll the ball with your legs so that rather than resting your shins on top of it, you are resting your toes on top of it. After reaching the peak position, you will again lower your buttocks back downward, rolling your shins back onto the top of the ball. After repeating a full set of Jackknife workouts, you may realize why some people choose this fairly difficult exercise over other abdominal workouts.