A Malaska Golf Member wants to understand the clubface staying at a 90-degree angle to the spine angle or sternum.
Mike elaborates on this question. He sets his club on the ground and then lifts it waist-high so the clubface is in line with his sternum. Then Mike sets up and swings his club a quarter of the way on his backswing. You will notice the clubface is in line with his sternum or at a 90-degree angle to his swing arc.
Mike continues to swing to the top and then on the backswing. At the three-quarter mark, the clubface is again on Mike's spine angle and at a 90-degree angle to his swing arc. He then runs the clubface into the ball. The clubface is parallel to Mike's sternum or at a 90-degree angle to his swing arc. Just like the backswing, it is the same on the follow-through. This is the physics of the golf swing.
If your golf swing works that way, you have a decent lever system, and your body keeps out of the way, it is easy to hit the ball straight.
The more the clubface twists at a 90-degree angle, the harder it is to time hitting the ball at impact. You can play that way, but it is more complicated.