Improving a pitcher’s knee kick
The human arm is not the strongest part of your body.
That’s why there are so many arm injuries in baseball. It’s not really designed for the stress we give it when we throw overhand. Because of that, pitchers must use their mid-section (just above the knees to the chest) where our strongest muscles are located. Use these muscles more and you can use your arm less. Use your arm less and you reduce the chance of injury.
Improving a pitcher’s leg kick can go a long way in getting more out of their mid-section. The two quickest ways to do that are as follows:
Bring the knee up to at least parallel. To get more out of their legs, pitchers need to raise their knee high enough so that the line from their knee back to their hip is at least parallel to the ground. Some pitchers can effectively go higher than that but no pitcher should go below that line in order to utilize more of their power muscles.
Line up the knees. Along with bringing their knee up to at least parallel, pitchers need to bring the knee back far enough so that the knees line up. Doing so turns the body in a way very similar to how a hitter loads up by going back before striding. Not lining the knees up tends to make the pitcher go forward before they have been able to gather their weight back fully.
The photo above shows both things correctly – a parallel knee kick and a lining up of the knees. Do both and you are on your way to a better use of your body when pitching.