Why can i see all my veins in my legs?

ive always been able to see some, im pale so its expected. but since i started track a month ago, like you can see every vein in my leg. im not fat and have some muscle tone, so why are my veins all of a sudden so visible? like my legs are all liney and my feet are like covered with bluish veins on the side. i had rlly bad shin splints too recently does that have anything to do with it? am i sick?