This may seem contridictory at first, but it does work.
If you want to start running distances faster just get some weights, start low like around 3-4 lbs per weight. Scuba weights work really good. First thing you need to do is run a certain distance, lets say 100yds. Record your time. then strap the weights to your legs. i started out with 3 3lb weights on each leg.
Start practicing running that 100yds with the weights attached to your legs. it will take some time but eventually you should be able to run the 100yds in about the same amount of time, because what happens is your legs become accustomed to the extra weight and your mussels will become stronger.
Just keep increasing your weight, but don't go above like 30 extra lbs on each leg or you might hurt yourself
my times went from about 30 seconds to just under 21 seconds. But it took me an entire summer of doing this style training.
~~~~~~~~~~I do not take responsibility if anyone gets hurt trying this, it worked for me but that doesn't mean it will work for you~~~~~~~~~~
if you think it was helpful