Jackknife Sit-Up

Jackknife Sit-Up

The Jackknife Sit-Up is an advanced abdominal exercise that targets the core muscles, particularly the rectus abdominis (the "six-pack" muscles) and the hip flexors. This challenging exercise is performed by lying flat on your back, extending your arms overhead, and lifting both your upper body and legs simultaneously, creating a V shape with your body. The key to performing a Jackknife Sit-Up effectively is to engage your core muscles throughout the movement. By initiating the movement from your abs rather than relying solely on momentum, you can maximize the effectiveness of this exercise. The Jackknife Sit-Up not only strengthens and tones your abs but also helps improve stability, balance, and overall core strength. It can be incorporated into a core training routine to enhance athletic performance or be part of a comprehensive full-body workout. Remember to start with proper form and increase the level of difficulty gradually to avoid any strain or injury. If you are a beginner or have any existing health conditions, it is recommended to seek guidance from a fitness professional before attempting this exercise.


  • Start by lying flat on your back on an exercise mat with your legs extended and arms overhead.
  • Simultaneously lift your arms and legs off the ground while curling your torso upwards.
  • Contract your abdominal muscles at the top of the movement.
  • Slowly lower your arms and legs back down to the starting position.
  • Repeat for the desired number of repetitions.

Tips & Tricks

  • Engage your core muscles throughout the exercise for maximum effectiveness.
  • Exhale as you lift your upper body and reach for your toes, then inhale as you lower back down.
  • Keep your neck relaxed and avoid pulling on it with your hands.
  • Maintain a slow and controlled movement to fully activate your abdominal muscles.
  • Focus on bringing your ribcage towards your pelvis rather than just reaching for your toes.
  • Use a mat or a towel to cushion your lower back and make the exercise more comfortable.
  • For an extra challenge, hold a dumbbell or medicine ball in your hands while performing the Jackknife Sit-Up.
  • To avoid strain on your lower back, make sure to engage your glutes and avoid arching your lower back too much.
  • Incorporate variation into your routine by trying different types of sit-ups, such as bicycle crunches or Russian twists.
  • Ensure proper form by practicing in front of a mirror or asking a fitness professional for feedback.


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