How to do the Jackknife Sit-ups
Primary: Core · also works Obliques, Hip Flexors.
Jackknife sit-ups, also known as V-ups, are an advanced core exercise that engages the abdominal muscles, hip flexors, and obliques. This exercise requires coordination and balance, making it an excellent choice for developing a stronger, more stable core.
Step by step
- 1
Lie flat on your back with your arms extended overhead and legs straight.
- 2
Simultaneously lift your legs and upper body off the ground, reaching your hands toward your feet.
- 3
Pause briefly when your hands and feet meet, then slowly lower back to the starting position.
Coaching cues
- Maintain a smooth and controlled motion throughout the exercise.
- Keep your core engaged to avoid straining your lower back.
- Breathe out as you lift your body and breathe in as you lower it.
Sets, reps and where it fits
Muscle
3–4 × 10–15
rest 60–90 s
Strength
4–5 × 4–6
rest 2–3 min
Fat loss
3 × 10–15
rest 45–60 s
Jackknife Sit-ups alternatives
Same movement pattern, different equipment or difficulty. Swap one-for-one in any plan.
Frequently asked questions
What muscles does the Jackknife Sit-ups work?
Primary: Core. Secondary: Core, Obliques, Hip Flexors
How many sets and reps of Jackknife Sit-ups should I do?
For muscle: 3–4 sets of 10–15 reps. For strength on compound lifts: 4–5 sets of 4–6. Rest 60–120 seconds between sets.
What can I do instead of the Jackknife Sit-ups?
Same movement pattern, different equipment: Bicycle Crunch, Bird Dog, Crunch, Dead Bug, Flutter Kick, Lying Leg Raise.
Is the Jackknife Sit-ups good for beginners?
With some training experience, yes. Beginners should start with one of the easier alternatives listed and progress to it.