A short crunch done with the soles of the feet pressed together and the knees dropped out to the sides. The frog-leg position takes the hip flexors out, leaving the abs to do the curl.
Primary muscles
Secondary muscles
This information is general fitness guidance, not medical advice. Stop if you feel pain and consult a qualified professional.
Main muscles working (thicker lines)
Lie on your back, press the soles of your feet together with the knees dropped out in a diamond and heels pulled in, and cross your arms to touch the opposite shoulders.
Brace your abs and flatten your lower back into the floor.
Curl your head and shoulders up through the first quarter of a sit-up, keeping your outer thighs low.
Hold the top for a second.
Lower slowly back to the start.
Breathing: Exhale as you curl up, inhale as you lower.
Soles together, knees wide
Flatten the back first
Small range, hard squeeze
Letting the knees rise to help
Sitting all the way up
Jerking with the arms or neck
Ease into the frog position if your hips or groin feel tight.