The C-shape in Pilates starts with a small pelvic tilt, then the ribs soften back and the deep core switches on. It’s not a slump; it’s controlled, supported flexion that creates space and helps you move with more control. Follow this video to master yours.

Set up

Sit upright with knees bent and feet flat on the floor, hip width apart.
Spine tall, weight evenly through the sit bones.
Arms can rest lightly on the thighs or out in front, palms facing at shoulder height. 
Optional ball between the knees for gentle stability, not squeezing.

Action

Initiate the movement with a (posterior) pelvic tilt, drawing the pubic bone gently up towards you.
From that tilt, roll back through the spine until you reach a point you can still control and breathe.
The C shape is created from the pelvis and lower spine, not by tucking the chin.
Pause, then return by reversing the move and sitting up tall to reset.