Jackknife Sit-up

Build solid, strong abs with this effective bodyweight exercise that targets the core.

Primary Muscle Abdominals
Secondary Muscle(s) None
Difficulty Intermediate
Also known as Jackknifes
Optional Ankle Weights

How to do Jackknife Sit-ups

  1. Lie flat on the floor with your arms fully extended back behind your head and you legs straight.
  2. Bend at the waist and contract your abs whilst simultaneously raising your legs and arms to meet in a jackknife position above your stomach. 
  3. 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.

Also see;


Always consult your GP before undertaking any form of weight loss, fitness or exercise.