Exercise guide
Cross Sit Up
- Beginner
- Compound
- Rep-based
- Waist
The Cross Sit Up is a dynamic core exercise that targets the rectus abdominis and obliques by combining a trunk flexion with a rotational component. This movement improves functional core strength and rotational stability by engaging the entire abdominal wall through a full range of motion.
Reviewed by the Crucible team · Updated June 2026
Muscles worked
Setup
- Lie flat on your back on a mat with your legs extended and feet hip-width apart.
- Place your fingertips lightly behind your ears or across your chest, keeping your elbows flared out.
- Engage your core by pulling your navel toward your spine and pressing your lower back into the floor.
How to do it
- Exhale as you sit up, rotating your torso to bring your right elbow toward your left knee.
- Simultaneously bend your left leg and pull the knee toward your chest so the elbow and knee meet over your midline.
- Inhale as you slowly lower your torso and leg back to the starting position with a controlled 2-second tempo.
- Repeat the movement on the opposite side, alternating for the duration of the set.
Form checklist
- Lead the rotation with your shoulder rather than just pulling your elbow forward.
- Keep your chin tucked slightly to maintain a neutral cervical spine and avoid neck strain.
- Ensure your lower back makes contact with the floor first during the descent.
- Avoid using momentum or swinging your arms to pull yourself up.
Pro tips
- Focus on the 'rib-to-hip' connection, visualizing your ribcage twisting toward the opposite hip bone for maximum oblique activation.
- Pause for a split second at the peak of the contraction to emphasize the mind-muscle connection in the obliques.
Make it harder
- Keep both heels hovered two inches off the floor throughout the entire set to maintain constant tension on the lower abs.
- Hold a light medicine ball or weight plate at your chest to increase the resistance during the sit-up and rotation.
Frequently asked
- What muscles does the cross sit up work?
- The cross sit up primarily targets the abs and obliques, and also works the erector spinae as secondary muscles.
- What equipment do you need for the cross sit up?
- The cross sit up requires no equipment — just your body weight.
- Is the cross sit up good for beginners?
- Yes. The cross sit up is a beginner-friendly movement and a strong foundation to build on.