Of course continuous proper training will help a lot, but only to a point. Talent/potential, or whatever you want to call it, counts for a lot. You give CF a slow, weak, uncoordinated, determined, 18 year old fat kid (say 40lbs overweight) and 4 years of training, and how fast do you think he could run the 100m at the end of those years? I would be impressed with 12.0.