There’s only so much satisfaction you can get out of a sit-up. Eventually, even the keenest crunchers will hanker for something new, something a little more challenging, to ensure their core is suitably tested with each workout. For those people, perhaps the best place to turn is the jackknife, the whole-body manoeuvre certain to leave your abs in a world of hurt.
As your aching midriff will no doubt testify, the jackknife is a real test for the abs. Your lower back also benefits from the manoeuvre, and you should find yourself becoming more flexible as the weeks of jackknifing go by. And one day you might even be able to keep your legs straight throughout the exercise – the optimum position.
How To Do It
Begin your jackknife by lying on the ground, with your arms outstretched behind your head. Keep your arms and legs raised a little off the ground throughout the movement. That movement is a simple one to understand, if not to do. Contract your abs and fold in two, bringing your arms and legs together to meet above your midriff, before easing them back to your starting position.
You’re aiming to keep your limbs as straight as possible throughout, but only the most flexible will be able to maintain straight legs, so don’t be too concerned if they bend a little on the way up. Try to build the jackknife into a circuits session to really ensure that your core doesn’t get off lightly.
The jackknife is a toughie, so don’t despair if it proves too hard to do more than a couple of reps of it at first. An easier variation that works the same muscles with less strain on the lower back is the modified V-sit.
Again, start by lying on your back with your feet raised, but keep your arms by your side this time. Then bend your knees and draw them towards your chest, sitting up at the same time, keeping your arms straight so that your hands end up by your feet. Then slowly unfold and return to the ground.