Exercise library · Abs

How to Do Jackknife Sit-Up

Step-by-step instructions, muscles worked and workouts that use the jackknife sit-up.

How to do it

1. Lie flat on the floor (or exercise mat) on your back with your arms extended straight back behind your head and your legs extended also. This will be your starting position.
2. As you exhale, bend at the waist while simultaneously raising your legs and arms to meet in a jackknife position. Tip: The legs should be extended and lifted at approximately a 35-45 degree angle from the floor and the arms should be extended and parallel to your legs. The upper torso should be off the floor.
3. While inhaling, lower your arms and legs back to the starting position.
4. Repeat for the recommended amount of repetitions.

Form tips

• Start light and own the movement before adding weight.
• Control the lowering phase — don't drop into it.
• Keep breathing; exhale on the hardest part.
• Stop if you feel sharp pain (different from muscle burn).

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Gear for this exercise

Exercise matGrip and comfort for floor work, core and stretching.See it on Amazon →Doorway pull-up barThe cheapest way to train your back and biceps at home.See it on Amazon →

Exercise photos and instructions: free-exercise-db (public domain). Animation made from the real start and end photos.