Jackknife Sit-Up

1. Start by lying flat on your back on an exercise mat with your arms extended overhead and legs straight out.

2. Engage your core and simultaneously lift your legs and upper body off the floor, reaching your hands towards your toes. Your body should form a V shape at the top of the movement.

3. Hold the contraction for a second and then slowly lower your body back to the starting position, without letting your limbs touch the floor.

4. Repeat the movement for the desired number of repetitions.

5. Keep the movements controlled, and make sure to breathe normally—exhale when you contract (lift) and inhale when you return to the starting position.

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