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Jackknife Exercise – Targeting the Abs and Lower Back to Improve Fitness

Jackknife Exercise

One of the best ways to get in shape is by trying new exercises. The Jackknife exercise is a brilliant choice, and it’s even better when you combine it with sit-ups. Jackknifes work your core muscles and train your lower back muscles, which are often neglected in workouts. However, jackknives require more than just a suitable form: you need to be dedicated and do daily exercises for maximum benefits!

The Jackknife exercise comes as one of the most exhilarating workout routines for you. The sit-ups, in and outs, and crunch exercise does core some justice, but the jackknife is a more challenging workout. The jackknife puts focus on the whole body and primarily targets the abs.

The jackknife exercise is beneficial for both abs and the lower back. After a few weeks of the jackknife exercise, you will see significant results. The optimum position for the movement is when you keep your legs straight during the activity. You can achieve significant results once you consistently perform the exercise daily.

How to do the jackknife exercise?

Start doing the jackknife exercise as you lie on the ground. Outstretch your arms and take them behind your head. Make sure your legs and arms are raising upward as you do the movement. This movement is quite simple to understand. You need to make sure you contract your abs and then fold in two. Bring your legs and arms together and meet above the midriff before moving them back towards the ground.

Keep your limbs straight as much as you can. However, only the most flexible people can maintain straight legs. Therefore, make sure you don’t focus on bending your legs too much as they rise. Instead, try building a jackknife in a circuit session to ensure that your core does not get off light.

The jackknife exercise is challenging. Therefore, don’t worry if it gets a bit too difficult at the beginning. A more straightforward modification of the movement will work your muscles with lesser strain on your back. This is the modified V-sit.

Also, you need to make sure you lie on your back and raise your feet. However, make sure that your arms stay at your sides this time. Now, you need to bend the knees and then draw them towards your chest. Next, sit up and keep your arms straight so that your hands touch your feet. Finally, unfold slowly and return to the start point.

Physical skills improved

The jackknife exercise is perfect for engaging your core and making it more stable. It helps you to perform activities well, such as running, rowing, and even swimming. If you want to learn more about the exercise, you can keep reading below. With a stronger core, you can also create a well-balanced body.

Muscles worked

The primary muscles involved in performing the jackknife include the internal oblique, rectus abdominis muscle, and external oblique muscle. The side jackknife trains the outer and inner oblique muscles. Another name for it is the oblique V-up.

Incorrect form

Many people put all their stress on their necks when doing the jackknife exercise. Stressing your neck will not result in more benefits. However, it will cause a strain on your neck. This is because your arms don’t have a connection with this exercise. It is more about the rectus abdominis muscle than anything else.

You need to keep your arms straight down beside you and not let them hover over the ground. This is to prevent a neck-pulling habit. Also, you can bring the arms up in a crunch state if you don’t feel that crunch as you do the exercise.

Imagine that there is a tennis ball between your chest and chin. Now, you need to keep the ball in shape as you perform the exercise. Your neck will experience an intense force if you put your chin towards the palate of your mouth. This will cause a sore neck that can lead to a headache.

You also need to make sure that your pelvis and the spine stay in a neutral position as you do the exercise. This will help to engage your core. Also, place the hip and pubic bones in a plane parallel to the ground. As you reach the pelvis in a neutral position, you will note the spine is creating a natural curve. As a result, you will maintain it as you do the crunch exercise.

Some people roll up towards the thoracic vertebra that is around the shoulder blades. Also, keep the pelvic region in a neutral position as you do the exercise. This will help you crunch up in a roll. However, don’t curl your neck and head forward; it will not keep your ab muscles in a proper position.

Some people do not expand their elbows wide enough to the side. As a result, the arms do not help you perform the jackknife exercise better. So, it is of no use to engage your pectoral muscles during the training. It will only preoccupy your mind and prevent you from doing the correct form and engaging all the abs.

Make sure you move slowly and steadily as you perform the exercise. Getting too speedy will only lead to a strain. You do not have to go fast; instead, you need to go slow and in a more controlling position not to use any momentum.


1. Supine leg raise

For this variation, you need to lie on the ground and keep your core tight. Now, bring your legs from the floor to a vertical position over your hips. Go back down once again. Grip something so you can make sure your core is stable. You can bend your knees up to 90 degrees.

2. Ab station leg raise

You will need to bend your knees in this exercise and don’t go down all the way. In addition, you need to make sure that your shoulders stay tight.

3. Pullup bar leg raises

This is a variation of the exercise, which includes grip strength limitation. You need to make sure that you do a small movement arc and bend your knees. However, don’t try doing this after or before any other exercise, which may tax your grip. This includes deadlifts, rows, and pullups.

You can also start in a plank position and keep the legs and the torso tight. Now, bend right at the hip and lift your hips. This will be the plank to the down-dog position.

4. Forearms in plank

Make sure your elbows are right under your shoulders. Clasp the hands together and do the same movement. It is the more extreme variation of abdominal exercise. The arms stay in an external rotating position because of the forearms. The forearms will stretch your lats and your shoulders. You may keep the hands in a joining position. Also, your arms will not be rotating externally to such an intense degree. Release the arms to sustain a broad supporting base as well as improve stability in the shoulders.

5. Gym ball exercise variation

You will need to keep your body forming a straight line rising from your head to your feet. Also, your hands need to be beneath your shoulders. Then, roll your feet over the gym ball. Finally, draw the knees towards your chest.

Last Word

The jackknife is one of the best ways to get in shape. It works your core muscles, train your lower back muscles, which you often neglect in workouts, and they’re exhilarating! If you want to try something new that will impact your fitness routine, you can’t beat these exercises. However, it requires more than just a suitable form – you need to do it daily for maximum benefits. So what has been your experience with this exercise? Let us know in the comments below!

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