Race Walking has a long history and has appeared as an Olympic event since 1904 and at the Olympics is competed by men over 20km and 50km distances, women compete over the 20km distance only. Being very technical, the sport is best defined by the rules of its governing body, the IAAF, who describe race walking as 'a progression of steps so taken that the walker makes contact with the ground, so that no visible (to the human eye) loss of contact occurs.' Additionally 'the advancing leg must be straightened (i.e. not bent at the knee) from the moment of first contact with the ground until the vertical upright position.'
Each race is over a course made up of 1km or 2km loops, with between 5-8 judges positioned around the course from positions where they are able to monitor the walkers adherence to the rules. Each judge can give a competitor one warning and there is a board on the start/finish line showing if you have received any warnings. Any walker receiving three warnings will be shown a red disk by the chief judge and this will indicate disqualification.