Is sprinting speed a natural ability? How much can training realistically affect sprinting speed?

[Eric]

On my softball team, the people I play with and people on other teams regularly make comments about how fast I run. People tell me that they wish I could run as fast as I run and that they have tried to train to run faster, but did not have great results. I almost always beat out routine groundballs to infielders because they usually can't throw me out in time. I am not bragging, because I think I am a good player, but not a great player, and I wish I had a lot more power (I mainly hit singles and doubles and I can't hit it over the wall). My brother (31 years old) is not nearly as fast as I am (27 years old), which also seems strange because it seems like I am the only fast runner in my entire family. I am great at sprinting short distances, but I am terrible at long distance running. Also, I never really sprinted on a regular basis until about 6 years ago. This also seems strange, because it is like I discovered an ability that I never really knew that I had. Thanks for your imput.