I love this topic because I think it is critical. Clemens is my favorite example because it can be deceiving. His shoulder tilt at leg lift is directed downward pretty significantly. I think that this helps him get his momentum going before he tilts his shoulders back. To me, the backward shoulder tilt is required more for timing than for actual power. It is essential for creating a good spine angle at foot plant. From what I have seen, the guys who don’t have a backward tilting spine angle at foot plant tend to be the one’s who have real “elbowy” arm actions because the arm has to work too fast to catch up to the body. I am not sure if any of that makes sense to anyone, but here is how I would summerize.
Clemens makes two distinct and intentional moves with his shoulders. IMO, the forward tilt at leg lift is to initiate momentum and the backward tilt during the stride is to help with timing.
I would love to hear more thoughts on this.