I love Dr. Yeager's work - I own his DVDs and cannot recommend them highly enough to anyone out there who wants to learn more about the baseball swing. (Unfortunately, his DVD purchase page seems to be down at the moment.)

His description of the lower half mechanics in this video are exactly in line with how I teach hitters in our Hitting Program and Semi-Private Training groups. While we differ on how to turn the barrel of the bat to contact, I strongly believe in his ability to generate force from the ground up to create a powerful swing.

https://www.youtube.com/watch?v=embl3dPg3PU