jackknife sit-up

How to do this exercise

1. Step:1 Lie flat on your back with your legs extended and your arms overhead.
2. Step:2 Engage your core and lift your legs and upper body simultaneously, reaching your hands towards your toes.
3. Step:3 Pause for a moment at the top, then slowly lower your legs and upper body back down to the starting position.
4. Step:4 Repeat for the desired number of repetitions.