Weighted Crunch (bent knee)
- Músculo objetivo
- Rectus Abdominis
- Músculos sinergistas
- Obliques
- Equipamiento
- Stability ball
- Parte del cuerpo
- Waist
- Tipo
- Strength
The weighted crunch (bent knee) is a core strength exercise that targets the rectus abdominis — the muscle running vertically along the front of your abdomen — with the obliques assisting throughout the movement. You perform it lying back on a stability ball with knees bent, holding a weight plate or dumbbell at your chest or behind your head. The ball's curved surface increases the range of motion compared to a floor crunch, and the added load progressively overloads the abs for greater strength and definition.
Cómo hacer el Weighted Crunch (bent knee)
- 1Select a weight plate or dumbbell and sit on the center of a stability ball, feet flat on the floor about hip-width apart.
- 2Walk your feet forward until your lower back is supported by the ball and your torso is parallel to the floor — the ball should sit in the curve of your lumbar spine.
- 3Hold the weight at your chest with both hands, or extend your arms and hold it behind your head for a longer lever.
- 4Brace your core and plant your feet firmly so the ball stays stable throughout the set.
- 5Exhale and curl your upper body upward by contracting your rectus abdominis, lifting your shoulder blades away from the ball until your torso is roughly 30–45 degrees above horizontal.
- 6Hold the top position for one count, squeezing your abs without pulling on your neck or jerking the weight.
- 7Inhale and slowly lower your upper body back down, allowing your abs to stretch over the ball before beginning the next repetition.
- 8Complete all reps, then lower the weight to your chest before carefully sitting upright off the ball.
Consejos de técnica
- Keep your chin slightly tucked — imagine holding a tennis ball between chin and chest — to avoid straining your neck and ensure your abs, not your hip flexors, initiate the movement.
- Control the descent: the eccentric (lowering) phase over the ball is where the stretch and growth stimulus happens, so resist the urge to drop back quickly.
- Start with a lighter weight than you think you need; the instability of the ball reduces how much load you can safely control compared to a floor crunch.
- Drive your lower back into the ball as you curl up rather than leaving space between your spine and the ball — this anchors the movement and keeps the rectus abdominis under tension.
Errores comunes
- Pulling on the neck: interlacing fingers behind the head and yanking the head forward shifts stress from the abs to the cervical spine and reduces rectus abdominis activation.
- Using too much hip flexor: initiating the crunch by lifting the lower back off the ball rather than curling the ribcage toward the pelvis recruits the hip flexors instead of the target muscles.
- Rushing the movement: bouncing through reps uses momentum rather than muscular force, cutting the time under tension and reducing the training effect on the rectus abdominis.
- Incorrect ball position: sitting too far forward means your lower back isn't supported by the ball during the stretch, collapsing the extended range of motion that makes this variation superior to a floor crunch.
- Choosing too heavy a load: excess weight causes the torso to rock and the obliques to overcompensate, taking work away from the rectus abdominis and increasing the risk of losing control of the ball.
Preguntas frecuentes
What is the advantage of doing a weighted crunch on a stability ball versus the floor?
The stability ball allows your torso to extend below the neutral position at the start of each rep, increasing the range of motion through which the rectus abdominis works. A floor crunch stops at neutral because the floor blocks that extension, so the ball version loads the abs through a longer range and adds a stretch at the bottom of each rep.
How heavy should the weight be for a weighted crunch on a stability ball?
Choose a weight that lets you complete your target reps with full control and a deliberate tempo — typically 8–15 reps for hypertrophy. Because the ball introduces instability, most people need to reduce the load they would use for a flat-floor weighted crunch by 20–30 percent when starting out.
Where exactly should I hold the weight during this exercise?
Holding the weight at your chest shortens the lever arm and is the safer starting position. Holding it extended behind your head lengthens the lever, making the movement significantly harder; only move to this position once you can maintain a neutral neck and controlled tempo with the weight at your chest.
How do I keep the stability ball from rolling during the weighted crunch?
Plant your feet firmly flat on the floor, set them slightly wider than hip-width, and press your lower back into the ball throughout the movement. Performing the exercise against a wall — with the ball braced between your lower back and the wall — is a useful modification if you are new to stability ball training.
How many sets and reps should I do for the weighted crunch (bent knee)?
Two to four sets of 8–15 reps suits most strength and hypertrophy goals for the rectus abdominis. Rest 60–90 seconds between sets. Progress by adding a small amount of weight once you can complete the top of the rep range with perfect form across all sets.
