Exercise guide
Leg Extension Star Crunch
- Intermediate
- Compound
- Rep-based
- Waist
The Leg Extension Star Crunch is a dynamic core exercise that integrates rotational abdominal work with active quadriceps engagement. It builds functional core strength and hip flexor stability by combining a diagonal crunch with a straight-leg lift.
Reviewed by the Crucible team · Updated June 2026
Muscles worked
Setup
- Lie flat on your back with your arms and legs extended outward to form an 'X' shape on the floor.
- Press your lower back firmly into the ground to eliminate any arch in the lumbar spine.
- Position your feet hip-width apart and your arms slightly wider than shoulder-width.
How to do it
- Exhale and simultaneously lift your right arm and left leg toward the center of your body, crunching your torso upward.
- Reach your right hand toward your left toes, lifting your right shoulder blade completely off the floor.
- Squeeze your quadriceps to keep the rising leg perfectly straight throughout the extension.
- Inhale as you lower back to the starting position with a slow, controlled tempo, then repeat on the opposite side.
Form checklist
- Keep the non-moving limbs anchored or hovering slightly for stability.
- Ensure the moving leg stays locked at the knee to maximize quad activation.
- Avoid pulling on your neck; lead the movement with your chest and obliques.
- Maintain lower back contact with the floor as you return to the starting position.
Pro tips
- Focus on the 'diagonal' squeeze—try to bring your ribcage toward the opposite hip bone rather than just reaching with your arm.
- Pause for a half-second at the top of the crunch to maximize the peak contraction of the rectus abdominis.
Make it harder
- Keep all four limbs hovering 2-3 inches off the floor throughout the entire set to maintain constant tension.
- Add light ankle weights to increase the leverage and resistance for the quadriceps and lower abdominals.
Frequently asked
- What muscles does the leg extension star crunch work?
- The leg extension star crunch primarily targets the abs and obliques, and also works the quadriceps as secondary muscles.
- What equipment do you need for the leg extension star crunch?
- The leg extension star crunch requires no equipment — just your body weight.
- Is the leg extension star crunch good for beginners?
- The leg extension star crunch is rated intermediate. Build a base with simpler variations first, then progress to it with light load and strict form.