Go to a typical high school athletic contest where there are several photographers and you will see that some shoot from a normal standing position and some will be kneeling or even sitting. This is common to soccer, football, basketball and other sports. Does that make any difference? Yes, a huge one.
Getting low creates an upward angle for your shots and that makes the athletes seem larger and more impressive. The shorter the athlete, the more important it is to get low. Parents of little children, this means YOU! Sit down to shoot the little ones whether they are in an organized sport or just playing with the dog. BTW, there is nothing more fun than shooting the first t-ball game.
1/1250 sec, f/2.8, 400mm, ISO 200, Canon 1D Mark IV, Canon EF 400mm f/2.8L IS
Sometimes, I'll even lay on the ground just to be able to shoot up at the athlete. Here I wanted to view the long jumper against a lovely sky instead of a cluttered background. My head is barely a foot to the side of the rake used to smooth the pit. That position to the side also enabled me to shoot with the sun at a better angle (at my back) compared to the shots I was able to get just sitting at the end of the pit looking up the runway. Those images had a much more pronounced sun/shadow line running through the middle of the face/body.
1/1250 sec, f/2.8, 35mm, ISO 100, Canon 1D Mark IV, Canon EF 24-70 f/2.8L II
Additionally, having a unique angle to your images will make them more interesting to the viewer. Your pics should show them something they don't normally see. Sometimes that can be an overhead perspective but often a low angle will turn a good image into a "WOW" shot. Just be sure to avoid the cardinal sin of being boring.
1/1000 sec, f/2.8, 182mm, ISO 3200, Canon 1D X, Canon 70-200 f/2.8L IS II
Philip S. Zivnuska