Jack knife on Ball exercise animation (Mujer)

Jack knife on Ball

Músculo objetivo
Rectus Abdominis
Músculos sinergistas
Adductor Brevis, Adductor Longus, Iliopsoas, Obliques, Pectineous, Sartorius, Tensor Fasciae Latae
Equipamiento
Stability ball
Parte del cuerpo
Waist
Tipo
Strength

The jack knife on ball is a stability-ball core exercise that targets the rectus abdominis: from a push-up position with your shins on the ball, you roll your knees toward your chest. The iliopsoas, sartorius, tensor fasciae latae, obliques, and the adductors of the inner thigh assist the tuck and control the roll. It trains the abs dynamically while demanding balance and shoulder stability.

Cómo hacer el Jack knife on Ball

  1. 1Kneel behind a stability ball and lay your torso over it, then walk your hands forward along the floor until your shins rest on top of the ball.
  2. 2Set your hands directly under your shoulders, shoulder-width apart, arms straight, in a push-up position.
  3. 3Brace your core and align your body from head to heels, hips level and lower back flat.
  4. 4Exhale and pull your knees toward your chest by contracting your abs, letting the ball roll forward toward your hands.
  5. 5Stop once your knees are close to your chest and before your hips pike sharply toward the ceiling.
  6. 6Pause for a beat at the top and squeeze your rectus abdominis.
  7. 7Inhale and extend your legs slowly, controlling the ball as it rolls back to the start.
  8. 8Finish in a straight-body plank without letting your hips sag, then repeat for the desired number of reps.

Consejos de técnica

  • Keep your shoulders stacked over your wrists throughout so your arms carry your weight instead of drifting and loading the joints.
  • Use a 2–1–2 tempo: two seconds in, a one-second squeeze, two seconds out. A fast roll hands the work to momentum.
  • Keep your hips square and resist any twist as you tuck, which makes the obliques work to stop rotation.
  • If the ball wanders, set up in a corner or against a wall so it can only roll along one line while you learn the pattern.
  • Choose a ball that lets your shins sit level with your shoulders at the start — an oversized ball leaves your hips high and takes tension off the abs.

Errores comunes

  • Piking the hips high on every rep, which turns the movement into a hip-hinge balance drill and shifts the load onto the shoulders and hip flexors instead of the abs.
  • Letting the lower back sag in the extended position, which loads the lumbar spine and means the core has stopped bracing.
  • Dropping the legs back rather than extending them, which skips the eccentric and cuts the rectus abdominis' time under tension in half.
  • Setting the hands too far forward or behind the shoulders, which tilts your weight off the support base and makes the ball far harder to control.
  • Holding your breath through the tuck, which spikes intra-abdominal pressure and leaves you unable to brace consistently rep to rep.

Preguntas frecuentes

What muscles does the jack knife on ball work?

It targets the rectus abdominis. The iliopsoas, sartorius, tensor fasciae latae, obliques, adductor brevis, adductor longus, and pectineus assist by driving the knee tuck and stabilizing the roll.

How is the jack knife on ball different from a plank?

A plank is an isometric hold — the abs resist movement. The jack knife adds a knee tuck, so the rectus abdominis shortens and lengthens through a full range under load, and the rolling ball adds a balance demand a floor plank does not have.

How many sets and reps should I do?

Three to four sets of 10–15 controlled reps works well. Stop the set when the tuck shortens or the hips start to sag — quality of range matters more than the rep count here.

Is the jack knife on ball good for beginners?

Not as a starting point. You need a solid 45-second plank and comfort holding a push-up position first. Build up with floor planks and mountain climbers, then move to the ball.

How do I make the jack knife on ball harder?

Slow the tempo and add a two-second pause at the peak contraction, or walk your hands forward so the ball sits nearer your ankles and lengthens the lever. Tucking one leg at a time adds an anti-rotation challenge.

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