Why are the legs in a butterfly position instead of flat?

The butterfly position rotates the hips externally, which helps deactivate the hip flexors and forces the abdominal muscles to do more of the work.

Should I use an AbMat for this exercise?

An AbMat is recommended because it fills the gap between your lower back and the floor, supporting the natural curve of your spine and increasing range of motion.

Is this exercise better than a standard crunch?

The butterfly sit-up is more effective for building functional strength and endurance through a full range of motion compared to the limited range of a crunch.

How to Do Butterfly Sit Ups: Technique and Form Guide

Master the butterfly sit up to isolate your core and improve hip mobility with our expert step-by-step instructions and common mistakes to avoid.

How to Perform

Sit on the floor with your knees bent and your feet flat on the ground.
Open your knees out to the sides and press the soles of your feet together in a diamond shape.
Lie your torso back slowly until your shoulder blades touch the floor behind you.
Reach your arms overhead and tap the floor with your hands to complete the descent.
Engage your core to sit up forcefully, swinging your arms forward to create necessary momentum.
Continue to rise until your hands touch your toes or the floor in front of your feet.
Lower your spine back down to the ground one vertebra at a time to maintain control.

Common Mistakes

Tucking the chin too hard against the chest
Lifting the feet off the floor during the ascent
Rounding the lower back aggressively instead of maintaining a neutral spine
Moving too fast and losing muscle tension on the eccentric phase

Muscles Worked

Primary movers

Obliquus externus abdominis

Stabilizers

Rectus abdominis
Hip flexors
Transverse abdominis

Related Guides

3008 Abdominal Crunch — Core
Ab Roller — Core
Ab wheel — Core

Obliquus externus abdominis · Core