Mainly because most of the middle and long-distance races are concentrated in the first lane (because the curve in the first lane is the shortest), the runway in the first lane is damaged faster and the quality is different from other lanes. Therefore, eight finalists in the 100, 200 and 400-meter races were arranged in lanes 2-9 to ensure the fairness of the race. At the same time, it also reduces the use times of 1 road and reduces the damage degree.
In business competitions, people like golden league will directly let nine people compete together, which can increase the number of participants. People like golden league don't have preliminaries.
But the ninth road also has great shortcomings. In the process of sprint competition, the faster the opponent is, the faster he is. But you can't see your opponent in the ninth lane, so you can only run with yourself. Only absolute strength can win.
The arrangement of the track was decided by drawing lots according to the ranking of the preliminary contestants, so the ninth miracle of Liu Xiang in that year was the perfect embodiment of his own strength.