Legs · Bodyweight
Jackknife
How to do the jackknife, the muscles it works, and the mistakes to avoid. Pulled straight from the Kovo app's exercise library.
- Equipment
- Bodyweight
- Difficulty
- Beginner
- Logged as
- Weighted reps
- Movement
- Flexion
- Mechanic
- Isolation
How to do it
Lie flat on your back with arms extended overhead and legs straight. Simultaneously lift your torso and legs, reaching your hands toward your feet so your body folds into a V, then lower back down with control.
- 1Feel your abs and hip flexors fold the body into a V
- 2Reach your hands toward your feet at the top
- 3Lower both halves back down under control
Common mistakes
- Avoid yanking with momentum to throw yourself up
- Don't let your lower back slam into the floor on the way down
- Avoid bending the knees to shorten the lift
Muscles worked
The jackknife mainly works the lower abs and hip flexors, with the upper abs, obliques, and front delts assisting.
- Lower AbsPrimary
- Hip FlexorsPrimary
- Upper AbsSupport
- ObliquesSupport
- Front DeltsSupport
- TricepsMinor
- ForearmsMinor
Kovo programs the jackknife for you and tracks it every session.
We build your whole program, drop the right lifts into each workout, and adjust your weights as you get stronger. Free on iOS and Android.
More hips & adductors exercises
- How to do the butterfly stretch
- How to do the external rotation
- How to do the cable hip adduction
- How to do the internal rotation
- How to do the cobra pose
- How to do the core scrunch
Last reviewed June 2026.