We see a lot of pitchers that have limited Hip Internal Rotation on their lead (landing) leg which has been correlated to elbow injuries and will make it more difficult to lead leg block.The lead leg block is caused by rotating into the front hip which causes the knee to extend upon landing. Knee flexion after your front foot lands has been proven to decrease throwing velocity, so if it is difficult for your body to rotate through the lead hip (internal rotation), you may be limiting your potential velocity.