Jackknife Sit-Up
Tone your core with Jackknife Sit-Ups! This challenging exercise builds strength and definition. Get ready to feel the burn!
The Jackknife Sit-Up is a compound exercise that mainly works the core, with help from the shoulders. No equipment needed: it uses just your bodyweight.
Optional Equipment
Jackknife Sit-Up Muscles Worked
Primary
Abdominals (rectus abdominis); Obliques
Secondary
Front Shoulder (anterior deltoid); Hip Flexor (iliopsoas)
Jackknife Sit-Up Variations and Alternatives
How to do the Jackknife Sit-Up
Start by lying flat on your back on an exercise mat with your arms extended overhead and legs straight out.
Engage your core and simultaneously lift your legs and upper body off the floor, reaching your hands towards your toes. Your body should form a V shape at the top of the movement.
Hold the contraction for a second and then slowly lower your body back to the starting position, without letting your limbs touch the floor.
Repeat the movement for the desired number of repetitions.
Keep the movements controlled, and make sure to breathe normally—exhale when you contract (lift) and inhale when you return to the starting position.
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Jackknife Sit-Up FAQs
What muscles does the Jackknife Sit-Up work?
The Jackknife Sit-Up mainly works the core, with help from the shoulders. The main muscles are the rectus abdominis and obliques.
What equipment do you need for the Jackknife Sit-Up?
None. The Jackknife Sit-Up is a bodyweight exercise, so you can do it anywhere.
Is the Jackknife Sit-Up a compound exercise?
Yes. It's a compound movement, meaning it trains several muscle groups at once rather than isolating one.
What are some Jackknife Sit-Up variations and alternatives?
Similar exercises include the Band Jackknife Sit-Up, Oblique Jackknife, Half Jackknife and Floor Jack-Knife.
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