Johannes Vetter is a German athlete who specializes in the javelin throw. His personal record is almost 320 feet and 9 inches, which is a long distance to throw anything at all.
How does Vetter do it? He trains hard and trains smart, using the best techniques and equipment available. This includes weighted sleds designed specifically for javelin training. I think that he's using this specific model, which was allows for not only weight adjustment, but also calculates the velocity of each throw. Athletes can use this machine while seated or standing.
-via Massimo