Side Jackknife: Double Leg

Double side jackknife exercise is very similar to lateral crunch exercise, but with one big difference. When performing double side jackknifes it’s not enough to raise only your head and shoulders sideways a couple of inches from the floor. You have to move your legs slightly upward as well. Basically, you need to bring your torso and legs toward each other at the same time (simultaneously). The movement resembles a jack-knife. In this post you’ll find out everything you need to know about this great exercise.

Step-by-step exercise instructions

Perfect technique has to be maintained all the time for this exercise to be effective. Doing this exercise incorrectly may lead to injury or lack of achievement of your bodybuilding goal. It is therefore crucial that one performs this exercise using the proper form in order to get the best out from this great exercise.

STARTING POSITION: Lie on your left hip, legs together and fully extended. Place your left elbow against your body for support and your right hand behind your ear. Avoid pulling your neck up with your hand. This is your starting position.

side crunches with legs lift - side jackknife

MOVEMENT (ACTION): Use your oblique muscles to raise both legs and simultaneously bring your torso up. In other words, you are bringing your head toward your hips while simultaneously raising your legs up. Try to keep your legs together while lifting them up (not as shown on the image above). As you progress with this exercise, you can add a few counts to the hold at the top of the move. Lower in a controlled motion and repeat the movement until you have completed your set. Then execute the movement on the other side.

Double side jackknifes: video demonstration

This animation is designed to show you exactly how to perform double side jackknifes using perfect technique (proper form) so that you can get the most out of this great exercise that targets your oblique muscles.

Double Side Jackknife: Video Demonstration

Exercise variations

  • This movement can also be done on an incline board, holding on to the board with your free hand for support.
  • You can bring your torso and only one leg toward each other (single-leg side jackknife).
single-leg side jackknife

single-leg side jackknife

Key points & helpful hints

Here are some key points to take into account.

  • Bring your legs slightly forward to increase your range of motion.
  • Focus your mind on feeling the obliques do the work.
  • Make sure your upper body moves off the floor. Don’t move just your head.
  • Hold a total contraction at the top of each movement for a count of two (if possible).
  • You’re not aiming for a big lift (no more than six inches). The focus should be on getting your oblique contraction right. You will feel your muscles working immediately if you perform it correctly.
  • Aim to reduce the space between your ribs and hips.
  • The abdomen does not lift the legs at all, but the movement helps some people feel the muscles exercised being worked.
  • Do not begin your ab routine with double side jackknife exercise. It is better to end your abdominal workout with the obliques rather than starting with them because your priority should be to work the rectus abdominis.
  • Lie on your left side to work the right obliques and then switch to your right side to work the left obliques.

Muscles engaged

Double side jackknife exercise works the external and internal obliques, muscles that run along the sides of the upper and lower abdominal muscles.

  • Main muscle groups: internal and external obliques;
  • Secondary muscle groups: rectus abdominis, quadratus lumborum, muscles along the spinal column;
  • Antagonists: the same muscles on the other side of the body;

Replacement exercises for double side jackknife

Doing the same exercise over and over can be tiresome. There are plenty of exercises that target your oblique muscles. Finding the right replacement should be a piece of cake.

Closing thoughts about double side jackknife exercise

This is another valuable exercise for your obliques in which you raise both the legs and the trunk (elevating the upper portion of the torso) at the same time. When done correctly, double side jackknife is a safe and very effective exercise that targets not only your obliques but other core muscles as well. You can do it at home. Exercise mat is the only equipment that you need.

About Author

Hey! My name is Kruno, and I'm the owner and author of Bodybuilding Wizard. I started this website back in late 2014, and it has been my pet project ever since. My goal is to help you learn proper weight training and nutrition principles so that you can get strong and build the physique of your dreams!

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