A hot shoe flash unit, and knowing how to use it would sure help these photos, particularly because you can be close to the action. The first 2 runners are severely underexposed because of the back lighting and apparent use of matrix metering. all the other photos, expect the girl in the black shirt, are also under exposed to one degree or another.
Using flash for field sports is less useful because the light can't reach far enough to fill the shadows.
+1 on the weak compositional aspects of the photos.
I would recommend a lower camera perspective for 2 reasons:
1 - to minimize background distractions.
2 - to make the runners seem taller and more powerful.