Exercise Library
Rotating Jack Knife

The rotating jack knife is a variation of the jack knife sit-up that adds trunk rotation.
Lie on the floor with the legs extended straight and your hands at the sides or behind your head where you would place them for a sit-up or crunch. Simultaneously perform a sit-up with the trunk and bend your knees to lift them up, rotating the trunk to bring one elbow to the opposite knee.
Your balance should be such that you can pause when the knees and elbows meet and hold this position. Return to an extended body position without allowing the heels to touch the floor in between reps.
The rotating jack knife can be done with pauses at the bottom and/or top, and transformed into a V-up by keeping the legs extended and the hands extended overhead.

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