Height has nothing to do with how well or fast you run. The world's current fastest male marathon runner, Haile Gebrselassie, is only 5'3". What determines your speed is your composition of fast-twitch and slow-twitch muscle fibers, leg turnover, fitness level and musculoskeletal system. While we cannot change genetics, training will allow for better leg turnover, fitness gains and better development of energy levels and musculoskeletal system. Over time, this translates to greater speed.