Set up: Seated on a fitball or chair, feet in front of your knees. Spine should be in neutral with shoulders back and down.
Keep upright but relaxed, let go through abdominals and pelvic floor. Place one hand on lower yummy, the other on lower back. Lift pelvic floor, gently draw in lower abdominals and hold whilst you continue to breathe normally. Make sure you are breathing into your sides (avoid chest and belly breathing) and keep your body relaxed, avoid tensing through legs, glutes and torso.
Use hands to feel core engagement, and to ensure low back position remains unchanged.