Balancing Jackknife Exercise

Written By: Todd Kuslikis
October 06, 2011

Jackknife Exercise (also known as Jackknife Sit up) is a unique way to develop core muscle strength. It engages both the lower abs and upper abs as your body does a jackknife like movement.

How to do it:

To perform the Jackknife Exercise, sit on the edge of a chair. Place your hands on the sides. Make sure your back is straight. Lift your legs up into the air while simultaneously crunching your upper body toward your rising knees. Again, your body will look like a jackknife as it folds together. Bring your upper body and your lower body back to starting position. Repeat.

Muscle group worked:

Lower abs, upper abs, obliques

Target Repetitions for Muscle Growth: 6-8

Target Repetitions for Muscle Tone/Endurance: 8-12

Why it works:

Since you are engaging both your upper and lower abs as your core jackknifes, it develops strengths throughout the abdominal region. By having your legs in the air, you are incorporating your lower abs. By crunching forward, you incorporate your upper abs.


To make the exercise easier, bring your feet closer to the chair. To make it more difficult straighten you knees.


Make sure to breathe out as your body jackknifes in and breath in as your body jackknifes out.


Disclaimer: Talk to your primary care physician before beginning any exercise regimen.

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1 Comment
  1. Lydia

    “To make it more difficult straighten you knees.” should be “To make it more difficult straighten your knees.”

    On most if not all of the exercise webpages you use breath instead of breathe for example:
    God gave Adam the breath of life.
    Breathe into this paper bag.

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