How to do Jackknife Sit-ups
- Lie flat on the floor with your arms fully extended back behind your head and you legs straight.
- Bend at the waist and contract your abs whilst simultaneously raising your legs and arms to meet in a jackknife position above your stomach.
- Lower your arms and legs back to the starting position and repeat.
Beginning the Jackknife Sit-up
If you can't yet perform the Jackknife Sit-up, try starting with the standard sit-up first or the plank and build up abdominal strength before progressing.
Advanced Jackknife Sit-ups
Weighted Jackknife Sit-ups
If you're starting to find the jackknife exercise particularly easy you can try introducing additional weight to the exercise. Hold a weight or medicine ball between your feet to add intensity as an effective technique for a seriously intense ab workout.