Jackknife Sit-Up
- Zielmuskel
- Iliopsoas, Rectus Abdominis
- Synergistenmuskeln
- Adductor Brevis, Adductor Longus, Obliques, Pectineous, Quadriceps, Sartorius, Tensor Fasciae Latae
- Equipment
- Body weight
- Körperregion
- Waist
- Typ
- Strength
The jackknife sit-up is a bodyweight core exercise that simultaneously contracts the iliopsoas and rectus abdominis by folding the body at the hips and waist. The quadriceps, obliques, and hip flexor muscles — including the sartorius and tensor fasciae latae — assist in controlling both the leg lift and the torso crunch. It is effective for building integrated hip flexor and abdominal strength with no equipment required.
Jackknife Sit-Up: So führst du sie aus
- 1Lie flat on your back with your legs fully extended and your arms stretched overhead, resting on the floor.
- 2Keep your lower back in contact with the floor and brace your core before initiating the movement.
- 3In one controlled motion, raise both straight legs and your torso simultaneously off the floor, reaching your hands toward your feet.
- 4At the top, your body should form a V-shape with your hips as the pivot point and both hands reaching as close to your feet as your flexibility allows.
- 5Hold the peak contraction briefly, squeezing your abs and hip flexors.
- 6Slowly lower your legs and torso back to the starting position in a controlled, simultaneous descent.
- 7Let your arms and legs return fully to the floor before beginning the next rep.
Technik-Tipps
- Lead the movement from your core rather than throwing your arms or swinging your legs — momentum reduces muscular tension.
- Keep your legs as straight as possible throughout the movement to maximize engagement of the hip flexors and quadriceps.
- Exhale as you fold into the jackknife position and inhale on the way down to maintain intra-abdominal stability.
- If your lower back peels painfully off the floor during the descent, slow the eccentric down — this is where core control matters most.
Häufige Fehler
- Using momentum by swinging your arms and legs at the same time, which shifts the work away from the abs and hip flexors and reduces the training stimulus.
- Bending the knees during the lift, which shortens the lever and decreases the demand on the rectus abdominis and iliopsoas.
- Letting your lower back arch aggressively off the floor at the start of the rep, which can place undue stress on the lumbar spine.
- Lowering your legs and torso at different speeds instead of simultaneously, which disrupts the symmetrical folding pattern the exercise is built on.
Häufig gestellte Fragen
What muscles does the jackknife sit-up work?
The primary muscles are the iliopsoas and rectus abdominis. The quadriceps, obliques, sartorius, adductors, pectineus, and tensor fasciae latae all assist in controlling the movement.
How is the jackknife sit-up different from a regular sit-up?
A standard sit-up only raises the torso while the legs stay on the floor. The jackknife sit-up lifts both the legs and the torso simultaneously, which greatly increases hip flexor involvement and makes the exercise more demanding overall.
Can beginners do jackknife sit-ups?
The exercise requires a reasonable baseline of core and hip flexor strength. Beginners may find it helpful to first master hollow-body holds and standard sit-ups before attempting the full jackknife movement.
How many reps should I do per set?
For strength and muscular endurance, sets of 10–20 controlled reps are common. Prioritize full range of motion and slow eccentrics over high rep counts with poor form.
Is the jackknife sit-up safe for people with lower back issues?
The movement places notable load on the hip flexors and lumbar spine, particularly if performed with poor control. If you have a history of lower back problems, consult a healthcare professional before adding it to your routine.
