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Exercise 0507 · REF mbkgB44

Jackknife Sit-Up exercise animation

Jackknife Sit-Up

Category
Waist
Equipment
Body Weight
Target
Abs

The jackknife brings the torso and legs up to meet in the middle simultaneously, which demands more from the abs than a standard sit-up where only the torso moves. It's a harder variation precisely because both ends of the body are working against gravity at once instead of one end staying anchored.

How to Do the Jackknife Sit-Up

  1. Lie flat on your back with your legs extended and your arms overhead.
  2. Engage your core and lift your legs and upper body simultaneously, reaching your hands towards your toes.
  3. Pause for a moment at the top, then slowly lower your legs and upper body back down to the starting position.
  4. Repeat for the desired number of repetitions.

Muscles Worked

The Jackknife Sit-Up primarily targets the Abs, with Hip Flexors as the primary synergist muscle group.

More Waist Exercises

3/4 Sit-Up 3/4 Sit-Up Body Weight · Abs 45° Side Bend 45° Side Bend Body Weight · Abs Air Bike Air Bike Body Weight · Abs Alternate Heel Touchers Alternate Heel Touchers Body Weight · Abs Arm Slingers Hanging Bent Knee Legs Arm Slingers Hanging Bent Knee Legs Body Weight · Abs Arm Slingers Hanging Straight Legs Arm Slingers Hanging Straight Legs Body Weight · Abs

More Abs Exercises

Arms Overhead Full Sit-Up (male) Arms Overhead Full Sit-Up (male) Body Weight · Abs Assisted Hanging Knee Raise Assisted Hanging Knee Raise Assisted · Abs Assisted Hanging Knee Raise With Throw Down Assisted Hanging Knee Raise With Throw Down Assisted · Abs Assisted Lying Leg Raise With Lateral Throw Down Assisted Lying Leg Raise With Lateral Throw Down Assisted · Abs Assisted Lying Leg Raise With Throw Down Assisted Lying Leg Raise With Throw Down Assisted · Abs Assisted Motion Russian Twist Assisted Motion Russian Twist Medicine Ball · Abs

Equipment Alternatives

Don't have body weight? These target the same abs with different equipment.

Assisted Hanging Knee Raise Assisted Hanging Knee Raise Assisted · Abs Assisted Motion Russian Twist Assisted Motion Russian Twist Medicine Ball · Abs Band Alternating V-Up Band Alternating V-Up Band · Abs Barbell Press Sit-Up Barbell Press Sit-Up Barbell · Abs

FAQ

What muscles does the Jackknife Sit-Up work?
The Jackknife Sit-Up primarily targets the abs, with the hip flexors as the main supporting muscle group.
What equipment do I need for the Jackknife Sit-Up?
The Jackknife Sit-Up is done with no equipment — just body weight.
What's a good alternative to the Jackknife Sit-Up?
If you don't have access to the space or setup it needs, the Assisted Hanging Knee Raise targets the same abs using assisted instead.