Gym, core
Hold a straight line from head to heels on your forearms. The timer only runs while your form is good.
Best on camera: a slow, steady move with your joints in clear view.
Phone at hip height, about 3 metres away, filming you from the side.
Your whole body, head to feet, needs to be in the picture. The coach will remind you if it can't see you.
Hips sagging
Squeeze your glutes and pull your belly button in.
Hips too high
Lower your hips until you're in one straight line.