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 core strength exercise that targets the rectus abdominis by drawing your knees toward your chest while your shins rest on a stability ball. The hip flexors — including the iliopsoas, sartorius, and tensor fasciae latae — along with the obliques and inner-thigh adductors assist in controlling the rolling motion, making it an effective compound ab exercise that also challenges balance and stability.

Cómo hacer el Jack knife on Ball

  1. 1Place a stability ball on the floor and kneel behind it. Roll forward over the ball until your shins rest on top of it and your hands are planted on the floor directly under your shoulders in a push-up position.
  2. 2Brace your core and align your body in a straight line from head to heels, keeping your hips level and your back flat.
  3. 3Exhale and pull your knees toward your chest by contracting your abs and hip flexors, allowing the ball to roll forward toward your hands.
  4. 4Continue rolling until your knees are tucked as close to your chest as your range of motion comfortably allows, keeping your hips from rising too high.
  5. 5Pause briefly at the top of the contraction, feeling the squeeze in your rectus abdominis.
  6. 6Inhale and slowly extend your legs back to the starting position, controlling the ball as it rolls away from you.
  7. 7Return to a straight-body plank position without letting your hips sag, and repeat for the desired number of reps.

Consejos de técnica

  • Keep your shoulders stacked directly over your wrists throughout the movement to avoid placing excess strain on your joints.
  • Keep your neck neutral by looking at the floor slightly ahead of your hands rather than craning back to watch the ball.
  • Engage your obliques by keeping your hips square and preventing any rotation as you tuck your knees in.
  • If you struggle with balance, start with a partially deflated ball to create a slightly more stable surface before progressing to a fully inflated one.

Errores comunes

  • Letting your hips pike too high during the tuck, which shifts the work away from the abs and onto the shoulders and hip flexors.
  • Allowing your lower back to sag in the extended position, which strains the lumbar spine and removes core tension.
  • Rushing through the extension phase, which reduces time under tension for the rectus abdominis and makes the movement less effective.
  • Placing your hands too far forward or behind your shoulders, which destabilizes the body and makes controlling the ball much harder.

Preguntas frecuentes

What muscles does the jack knife on ball work?

The primary muscle is the rectus abdominis. The iliopsoas, sartorius, tensor fasciae latae, adductor brevis, adductor longus, pectineus, and obliques all assist in controlling the knee tuck and stabilizing the movement.

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

Unlike a static plank, the jack knife on ball adds a dynamic knee-tuck motion that actively contracts the rectus abdominis through a full range of motion. The rolling stability ball also demands greater balance and core coordination.

How many reps should I do for the jack knife on ball?

For strength and hypertrophy, aim for 3–4 sets of 10–15 controlled reps. Focus on quality and full range of motion rather than speed or high rep counts.

Is the jack knife on ball suitable for beginners?

It requires a solid foundation in core stability and plank holds, so it is better suited to intermediate exercisers. Beginners should first build comfort with standard planks and basic stability ball exercises before attempting it.

Can I make the jack knife on ball harder?

Yes — slow down the tempo, pause longer at the peak contraction, or set up with the ball under your toes instead of your shins, which lengthens the lever and increases the demand on your abs. Single-leg tucks add a further balance challenge.

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