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Folding knives / jackknife / V-ups

The exercise known as scissor movement in the fitness domain enjoys great popularity when it comes to strengthening the abdominal muscles. There are various terms for this particular abdominal exercise. Within the German-speaking context, the term scissor movement has become widely adopted. However, expressions like spread jump, spread sit-ups, or knife jump are also common in the gym.

The scissor movement offers various training possibilities, which will be presented in detail in the following section. The training stimulus primarily focuses on the straight and pyramidal abdominal muscles. It is often emphasized that the scissor movement is considered risky, and the risk of injury may outweigh the benefits. This is because a significant part of the movement originates from the hip flexor, which tends to shorten. Every athlete should independently assess whether and to what extent the scissor movement should be integrated into their training plan.

Muscles stressed during V-ups

During spread jumps, the primary muscles trained are the straight abdominal muscle (musculus rectus abdominis) and the pyramidal muscle (musculus pyramidalis). The oblique abdominal muscle (musculus obliquus abdominis) acts as supporting musculature to ensure optimal execution of the movement.

Folding knife on the ball

The exercise called Ball Jacket in Jackknife can be performed not only as a variation of crunches or sit-ups. Simultaneously, there is the option to practice the Ball Jackknife on a gym ball. The ball opens up various possibilities for fitness training. Popular variations in ball training include upper body bending on the ball, crunches with the ball, or sit-ups with the ball. However, the next section focuses on the correct body position and execution on the ball.

Body Position

Take a gym ball and place it on the floor. The starting position is similar to a push-up. Your hands are under the chest and remain there throughout the entire exercise. The gaze is directed downward so that your head is in a natural extension of the spine. The feet and legs up to the height of the knee rest on the ball. Your body forms a straight line. Tension in the body is maintained throughout the entire exercise.

Execution of Movement

Start the exercise by pulling the ball toward you with your feet and lowering the knees. This moves your buttocks slightly upward, and the thighs are lowered downward. The shins continue to press on the ball. Thighs and shins should not form a right angle. The gaze goes a bit further down. Exhale during this movement. Then push back into the starting position, where the entire body is almost straight.

Jack Split Crunch

Another variation of the Ball Jacket exercise is the Jack Split Crunch. To fully maximize the potential of the exercise and ensure flawless execution, you will find additional information on body position and movement execution here.

Body Position

For Jack Split Crunches, start in the lying position. The arms are stretched backward above the head and are in a position parallel to the ground. The legs lie flat on the ground, and the gaze is directed upward.

Execution of Movement

Start the exercise by exhaling, lifting the upper body, and raising your legs. The hands move through the center of your legs toward the ground. You can execute the movement as far as possible. Then return to the starting position while inhaling deeply. Keep your back straight throughout the entire exercise. It's better to reduce the range of motion than to round your back.

Classic V-Ups

Conventional X-downward movements are relatively common in the gym. In the following section, you will receive comprehensive information about the optimal body posture and execution of the movement.

Body Posture

To begin, position yourself in the starting position by lying flat on your back. The legs are slightly apart. Extend your arms behind your head so that they run parallel to the ground in line with the rest of your body. The head forms a natural extension of the spine. The entire body forms an imaginary horizontal line. Your gaze is directed upward.

Execution of Movement

To initiate the traditional X-downward movements, lift your upper body and legs. Your legs reach almost a 90-degree angle. Execute the movement as far upward as you can perform it correctly. Simultaneously, straighten your upper body. Pull your hands toward your toes during this upward movement. Exhale during this upward motion. Then return to the lying position, not fully lowering your arms and legs.

Common Jackknife Mistakes

A precise execution of the knife folding exercise is of particular importance. Errors during the execution can increase the risk of injury and compromise the success of the training. In the following section, various sources of errors are highlighted, along with tips on how to avoid them.

✅ Hunched back during execution: Throughout the entire movement, your back should maintain a straight posture. It is crucial to avoid hunching the back.

✅ Proper breathing technique: Breathing plays a crucial role in the knife folding exercise. When lifting arms and legs, exhale consciously. When lowering the legs, perform an inhalation.

✅ Avoid overextending the head: During the execution, avoid overextending the head. You should neither tilt your head backward nor press the chin to the chest.

Alternatives and similar exercises to the jackknife exercise

The effectiveness of the knife folding exercise is doubted by some athletes. Those who prefer not to incorporate it into their training routine can instead utilize the following alternatives to strengthen their abdominal muscles.

V crunches

V-Crunches are an exercise that bears clear similarities to knife folding. Here, the focus is also primarily on the rectus abdominis.

Lying Leg Raises

The execution of leg raises can be done in a lying or hanging variation. In this case, the movement is exclusively from the legs, unlike knife folding, where both the upper and lower body are involved.

Toe touch

Another abdominal muscle exercise is toe touches. The entire movement focuses on reaching towards your toe tips with your hands.

More sit-up variations

Sit-ups are the classic in abdominal muscle training. There are numerous variations that you can find on the overview page of abdominal exercises. Especially the classic sit-ups and the lateral variations are widely popular in the gym.