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Jackknife Sit-Up

Abdominals Beginner Strength Body Only
Jackknife Sit-Up Jackknife Sit-Up
Equipment
Body Only
Level
Beginner
Force
Pull
Mechanic
Compound
Instructions
  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.
Frequently asked questions
What muscles does the Jackknife Sit-Up work?

Jackknife Sit-Up primarily targets the Abdominals. This makes it an effective strength exercise for building abdominals development.

Do I need equipment for the Jackknife Sit-Up?

No. The Jackknife Sit-Up is a bodyweight exercise that requires no equipment. It can be performed anywhere with enough space.

Is the Jackknife Sit-Up suitable for beginners?

Yes. The Jackknife Sit-Up is a beginner-friendly exercise. Focus on proper form before adding weight or intensity. It's a great movement to include early in your training.

Is the Jackknife Sit-Up a compound or isolation exercise?

The Jackknife Sit-Up is a compound exercise, meaning it works multiple joints and muscle groups simultaneously. Compound movements are efficient for building overall strength and are typically performed earlier in a workout when you have the most energy.

How many sets and reps should I do for the Jackknife Sit-Up?

For strength, aim for 3-5 sets of 5-8 reps with heavier weight. For muscle building (hypertrophy), try 3-4 sets of 8-12 reps at a moderate weight. For endurance, use lighter weight and perform 2-3 sets of 15-20 reps.

What are good alternatives to the Jackknife Sit-Up?

Good alternatives include the 3/4 Sit-Up, Ab Crunch Machine, Ab Roller. These exercises target similar muscle groups (Abdominals) and can be substituted based on available equipment or training preference.

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