Exercise guide
Cocoons
- Advanced
- Isolation
- Rep-based
- Lower arms
- Upper arms
- Waist
Cocoons are a comprehensive core movement that integrates a crunch and a leg tuck to target the entire abdominal wall and hip flexors simultaneously. This exercise builds functional core strength and stability by requiring constant tension throughout a full range of motion.
Reviewed by the Crucible Fit team · Updated June 2026
Muscles worked
Setup
- Lie flat on your back on a mat with your legs fully extended and arms reaching straight overhead.
- Engage your core to press your lower back firmly into the floor.
- Lift your heels and hands 2-3 inches off the ground to establish a 'hollow body' starting position.
How to do it
- Simultaneously pull your knees toward your chest while swinging your arms forward in a circular motion toward your feet.
- Exhale as you crunch your upper body up, aiming to 'tuck' into a tight ball with your hands reaching past your shins.
- Inhale as you slowly reverse the movement, extending your arms and legs back to the starting position.
- Maintain a controlled tempo, ensuring your limbs do not touch the floor between repetitions.
Form checklist
- Keep your lower back in contact with the floor at all times, especially during the extension.
- Avoid using momentum to swing your limbs; focus on abdominal contraction.
- Keep your chin tucked slightly toward your chest to maintain a neutral cervical spine.
- Ensure full extension of the legs to maximize hip flexor and lower abdominal engagement.
Pro tips
- At the peak of the tuck, visualize pulling your belly button into your spine to maximize the contraction of the deep transverse abdominis.
- Squeeze your glutes as you extend your legs to help stabilize the pelvis and prevent your lower back from arching.
Make it harder
- Hold a light medicine ball or dumbbell between your hands to increase the lever length and resistance.
- Perform the eccentric (extension) phase over a 4-5 second count to significantly increase time under tension.
Frequently asked
- What muscles does the cocoons work?
- The cocoons primarily targets the abs and obliques, and also works the erector spinae, lats, and triceps as secondary muscles.
- What equipment do you need for the cocoons?
- The cocoons requires no equipment — just your body weight.
- Is the cocoons good for beginners?
- The cocoons is rated advanced. Build a base with simpler variations first, then progress to it with light load and strict form.