<P> The origin of this event comes from the need to transport the bulls from the fields outside the city, where they were bred, to the bullring, where they would be killed in the evening . During this' run', youngsters would jump among them to show off their bravado . In Pamplona and other places, the six bulls in the event are still those that will feature in the afternoon bullfight of the same day . </P> <P> Spanish tradition says the true origin of the run began in northeastern Spain during the early 14th century . While transporting cattle in order to sell them at the market, men would try to speed the process by hurrying their cattle using tactics of fear and excitement . After years of this practice, the transportation and hurrying began to turn into a competition, as young adults would attempt to race in front of the bulls and make it safely to their pens without being overtaken . When the popularity of this practice increased and was noticed more and more by the expanding population of Spanish cities, a tradition was created and stands to this day . </P> <P> The Pamplona encierro is the most popular in Spain and has been broadcast live by RTVE, the public Spanish national television channel, for over 30 years . It is the highest profile event of the San Fermin festival, which is held every year from 6--14 July . The first bull running is on 7 July, followed by one on each of the following mornings of the festival, beginning every day at 8 am . Among the rules to take part in the event are that participants must be at least 18 years old, run in the same direction as the bulls, not incite the bulls, and not be under the influence of alcohol . </P> <P> In Pamplona, a set of wooden fences are erected to direct the bulls along the route and to block off side streets . A double wooden fence is used in those areas where there is enough space, while in other parts the buildings of the street act as barriers . The gaps in the barricades are wide enough for a human to slip through but narrow enough to block a bull . The fence is composed of approximately three thousand separate pieces of wood . Some parts of the fence remain in place for the duration of the fiesta, while others are placed and removed each morning . Spectators can only stand behind the second fence, whereas the space between the two fences is reserved for security and medical personnel and also to participants who need cover during the event . </P>

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