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Jack knife

A core exercise that combines a leg raise with a crunch movement to target the abdominal muscles and improve core strength and flexibility.

Exercise Overview

Category

Isometric Calisthenics

Exercise_Type

Strength

Difficulty_Level

Intermediate

Technique

Lie on your back with arms extended overhead and legs straight. Simultaneously lift your upper body and legs, bringing your hands toward your feet in a V-shape, then return to starting position.

Starting Position

Begin lying on your back with arms extended overhead and legs straight on the ground.

Finishing Position

Return to the starting position with arms overhead and legs straight after completing the jack knife movement.

Form Cues

Lift both upper body and legs, reach toward feet, engage core, control the movement

Common Mistakes

Using momentum, not feeling core engagement, poor form, incomplete movement

Progression Tips

Add weight, increase reps, or perform more advanced variations.

Regression Tips

Bend knees, reduce range of motion, or perform separate leg raises and crunches.

Safety Notes

Maintain proper form to avoid lower back strain. Stop if you experience pain in the lower back or neck. Keep your core engaged throughout the movement.