400 m hurdles

One lap with ten hurdles. The barriers are 0.914 metres high for men and 0.762 metres for women; the first stands 45 metres from the start, the rest come every 35 metres, and 40 metres remain to the line. Runners keep a set number of strides between hurdles, often 13 to 15, and the hard part is changing that pattern on the bends as the legs tire, which means hurdling off the other leg without breaking rhythm. Being able to lead with either leg is what separates the specialists from the fast 400-metre runners who try the event. Knocking a hurdle over costs nothing unless it is done on purpose. There is no wind reading over a full lap.