Exercise guide
Dumbbell Starfish Crunch
- Beginner
- Compound
- Rep-based
- Waist
This dynamic core exercise targets the entire abdominal wall and obliques through a diagonal reaching motion, improving rotational stability and coordination. By using a dumbbell, it adds resistance to the upper body, increasing the demand on the deep core and hip flexors.
Reviewed by the Crucible Fit team · Updated June 2026
Muscles worked
Setup
- Lie flat on your back on a mat with your arms and legs spread wide, forming an 'X' or starfish shape.
- Hold a single light dumbbell in your right hand, resting your arm on the floor.
- Press your lower back firmly into the mat and engage your core to eliminate any arch in your spine.
How to do it
- Exhale as you simultaneously lift your right arm (holding the dumbbell) and your left leg toward the center of your body.
- Reach the dumbbell toward your left foot, lifting your right shoulder blade off the floor while keeping the non-working limbs grounded.
- Inhale as you slowly lower your arm and leg back to the starting position with a controlled 2-second tempo.
- Complete the desired number of repetitions on one side, then switch the dumbbell to your left hand to work the opposite side.
Form checklist
- Keep the moving arm and leg as straight as possible throughout the entire range of motion.
- Ensure your lower back stays in constant contact with the floor to protect your spine.
- Lead the movement with your abdominals rather than using momentum to swing your arm.
- Keep your neck neutral by looking diagonally upward rather than tucking your chin to your chest.
Pro tips
- Focus on the 'diagonal' crunch, feeling the tension move from one hip toward the opposite ribcage for maximum oblique activation.
- Squeeze your quadriceps to keep your legs locked out, which increases the lever length and makes the core work harder.
Make it harder
- Hover all four limbs 2 inches off the ground between repetitions to maintain constant tension on the core.
- Slow down the eccentric (lowering) phase to 4 seconds to increase time under tension.
Frequently asked
- What muscles does the dumbbell starfish crunch work?
- The dumbbell starfish crunch primarily targets the abs and obliques, and also works the erector spinae and serratus anterior as secondary muscles.
- What equipment do you need for the dumbbell starfish crunch?
- The dumbbell starfish crunch uses dumbbell.
- Is the dumbbell starfish crunch good for beginners?
- Yes. The dumbbell starfish crunch is a beginner-friendly movement and a strong foundation to build on.