It is essential for their own safety that props have the correct body alignment before the scrum engages. They can check, for instance, that their back is straight by crouching alongside a mirror, at home or in the gym. They can do this with their eyes closed, and then look in the mirror to see if the correct position has been achieved, and the forces from the players behind will be transferred forward in a straight line.
It can be really helpful to video one versus one scrums, so you can check that they have maintained the correct position on engagement. The players can view it themselves so they can confirm that their sensation of body position matches the reality.
The position of the head and neck are vital as it’s very easy to get into an unnatural position, and serious injury could result. Once the player is in the crouched position, you can get him to stand up straight, but making sure that his head and neck position are unchanged. Do they remain in a natural position? If the neck is unnaturally forward or back it is in an unsafe position.
One suggestion for finding the correct head position is to wear a pair of sunglasses. In the crouched position, you lift your head up until you can just see over the top of them. You check this as before by standing up and seeing if it still in a natural position.
One technique that can be really useful for props to get maximum power in the scrum is centring. This is a visualisation technique that involves putting the focus on the centre of your body. This makes the player more balanced, and therefore increases power, especially as the focus is on the area where there are larger, more powerful groups of muscles.
Getting into the correct body position is also very important in lifting at the lineout. A common fault is to allow the head to fall forward, so that the arms cannot lift straight up but at an angle, with the resulting loss of power and direction. Lifters also need to make sure that they keep forwards to their fellow lifter. If they look up, they are almost certain to tip back a bit and lose the ideal strong position for maximum lift.