Giraffes can run deceptively fast despite their long neck. They have an unusual leg action which coupled with the weight of their neck makes them rock backwards and forwards as they get up to speed. Not surprisingly their leg muscles are very powerful and they can kill a lion with a kick. Evolution has programmed them to be able to run as fast or slightly faster than the predator which hunts them and the only one capable of this is the lion. Top speed is up to 50mph but they can keep this up for much longer than the lion which is a sprinter not a long distance runner.