This Pitching Velocity Quick Tip covers an important factor of the "Load" position. This is a pitching component in the 3X mechanics. You can learn more about the 3X mechanics by watching this video on the 3X Pitching approach. The important factor of the "Load" position that will be covered here is drive leg flexion. Drive leg flexion is a critical part to the "Load" position because good flexion leads to good extension which is the next component in the 3X mechanics which is the foundation for the entire approach. Most young pitchers have poor flexion and also poor force production through that flexion.
To truely understand how flexion and force production work then I would highly recommend that you watch this video. If you want to see if you have good flexion and force production in your delivery then post your pitching video for analysis here at the forums.