# Jackknife Sit-Up

URL: https://heatsy.app/ex/jackknife-sit-up

Also known as: Jack-Knife Sit-Up, Jackknife Crunch, V-Up

Body region: Core, Legs

## Muscles

- Main: Rectus Abdominis, Iliopsoas
- Helps: External Oblique, Internal Oblique, Rectus Femoris
- Holds: Transversus Abdominis, Tensor Fasciae Latae

## Technique

1. Lie flat on your back with legs straight and arms extended overhead.
2. In one motion, lift the straight legs and the upper body together.
3. Reach the hands toward the feet so the body folds into a V at the top.
4. Lower both ends slowly back to the floor.

### Cues

- Keep the legs straight and lift them with the abs, not a kick.
- Exhale as you fold up.

### Common mistakes

- Swinging the arms to create momentum.
- Slamming the back and legs into the floor.
- Bending the knees to make the fold easier.

## Alternatives

- [Sit-Up](https://heatsy.app/ex/sit-up)
- [Vertical Leg Crunch](https://heatsy.app/ex/vertical-leg-crunch)
- [Hanging Leg Raise](https://heatsy.app/ex/hanging-leg-raise)