Gym, legs
The foundation of leg strength. Sit back and down as if into a chair, then stand tall.
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.
Too shallow
Sit lower, until your thighs are level with the floor.
Chest falling forward
Keep your chest up and push your hips back, not down.
Rushing
Take about 2 seconds down and 1 second up.