sprinter was disqualified if responsible for two false starts individually. However, this rule allowed some major races to be restarted so many times that the sprinters started to lose focus. The next iteration of the rule, introduced in February 2003, meant that one false start was allowed among the field, but anyone responsible for a subsequent false start was disqualified. This rule led to some sprinters deliberately false-starting to gain a psychological advantage: an individual with a slower reaction time might false-start, forcing the faster starters to wait and be sure of hearing the gun for the subsequent start, thereby losing some of their advantage. To avoid such abuse and to improve spectator enjoyment, the IAAF implemented a further change in the 2010 season – a false starting athlete now receives immediate disqualification. This proposal was met with objections when first raised in 2005, on the grounds that it would not leave any room for innocent mistakes. Justin Gatlin commented, "Just a flinch or a leg cramp could cost you a year's worth of work." The rule had a dramatic impact at the 2011 World Championships, when current world record holder Usain Bolt was disqualified. Mid-race Runners usually reach their top speed just past the halfway point of the race and progressively decelerate to the finish. Maintaining that top speed for as long as possible is a primary focus of training for the 100 m. Pacing and running tactics do not play a significant role in the 100 m, as success in the event depends more on pure athletic qualities and technique. Finish The winner, by IAAF Competition Rules, is determined by the first athlete with their torso (not including limbs, head, or neck) over the nearer edge of the finish line. There is therefore no requirement for the entire body to cross the finish line. When the placing of the athletes is not obvious, a photo finish is used to distinguish which runner was first to cross the line. Climatic conditions Climatic conditions, in particular air resistance, can affect performances in the 100 m. A strong head wind is very detrimental to performance, while a tail wind can improve performances significantly. For this reason, a maximum tail wind of 2.0 m/s is allowed for a 100 m performance to be considered eligible for records, or "wind legal". Furthermore, sprint athletes perform a better run at high altitudes because of