Core / Beginner / Compound (multi-joint)

Jackknife Sit-Up

A bodyweight exercise for the abs, with the hip flexors assisting.

At a glance

Primary

Abs

Secondary

Hip flexors

Equipment

Bodyweight

Movement pattern

Hip flexion, Trunk flexion

Level

Beginner

Type

Core, Compound (multi-joint)

Loads the lower back. Use a load you can control and skip it if it causes pain.

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.

Common mistakes

• ✗ Using a big jerk to get up.

  Why it hurts: The lower back and hip flexors are yanked fast.

  ✓ Instead: Lift the arms and legs together with control; bend the knees to make it easier.

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