it's a myth that people with long legs run faster. they think this because they think that long legs will cover more distance with the same stride length but they fail to realize that not only will such a thing decrease your cadence, but having long legs also means you have more weight and will have to fight more air resistance. one of the fun things in life is that the most optimized people for running are those with average height. now obviously there are some outliers. usain bolt and rudisha are on the taller side, but on average, it's you'd expect people who are outliers on the tall or short end of the spectrum to be slower.