Jackknife Sit-Up
How to do the Jackknife Sit-Up with correct form, the muscles it works, and where it fits a training plan you actually stick to.
Abs
,
Body Only
How to do the Jackknife Sit-Up
- 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.
Log it, see it on your body.
Every Jackknife Sit-Up set you log feeds Ascend's anatomy heatmap, so your abs volume is visible at a glance, and counts toward your bodyweight-strength tier.
Where the Jackknife Sit-Up fits
The Jackknife Sit-Up shows up in training built around a specific goal. See how it fits:
More abs exercises
Jackknife Sit-Up: common questions
What muscles does the Jackknife Sit-Up work?
The Jackknife Sit-Up primarily works the Abs.
Is the Jackknife Sit-Up suitable for beginners?
Yes. The Jackknife Sit-Up is a beginner-level exercise, so it's a solid choice if you're new to training. Start light and focus on the movement pattern before adding load.
What equipment do I need for the Jackknife Sit-Up?
None. The Jackknife Sit-Up is a bodyweight exercise, so you can do it without any equipment.
Is the Jackknife Sit-Up a compound or isolation exercise?
The Jackknife Sit-Up is a compound exercise, it moves multiple joints and works several muscle groups at once, which makes it efficient for building overall strength.
How do I do the Jackknife Sit-Up with correct form?
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. Follow the full step-by-step above for the complete movement.
Log your Jackknife Sit-Up sets, free.
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