Excerpt from the article:
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"Here is a quick summary:

2002: Earlier muscle activation allows improved dynamic balance in order to set up a better foundation for rotation. Slightly more vertical shoulder angle creates more opportunity direct the rotational momentum towards home plate via forwards flexion of the spine, and improves ability to 'get on top' of the ball for more downwards movement (sink).

2006: Weight back and reaching front foot leaves static balance over the rubber, possibly leads to opening up during rotation. This combined with the horizontal shoulder angle decreases opportunity to transfer rotational momentum into delivery towards home plate. Arm comes across the ball in a more horizontal plane, creating more lateral movement."
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