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  Bolt, who completed a sprint double in Beijing with Thursday's 200m win, added he would run at the 2016 Olympics.
  "I want to run but I think the sport is not as fun as it used to be - it's more taxing," the 29-year-old, who has won 10 world titles, told the BBC.
  "I can't enjoy it as much as I want to because I have to sacrifice more."
  He added: "It is 50-50."
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  Bolt could make his gold-medal tally to 11 this weekend when he competes for Jamaica in the 4x100m relay.
  Once again he is likely to face Justin Gatlin in the final, with the United States one of the favourites for gold. The Jamaicans were beaten by an American quartet at the IAAF World Relays in May.
  "In the World Relays, Justin Gatlin had a big game in their victory," added Bolt. "I guess he will be tired now. There will be no reason why we should not win the relay."
  Some media outlets have been accused of portraying Gatlin as the "villain" to Bolt's "hero" following two career doping bans.
  He came into the World Championships having set the best times over 100m and 200m this season.
  Bolt pipped Gatlin to the 100m title, before the American fell to a more emphatic defeat in the longer sprint on Thursday.
  Asked by BBC Radio 5 live if a double silver was a disappointment, Gatlin said: "Not at all. I'm out here competing. I'm aged 33.
  "I think a lot of people now see the hard work and effort I put into it. It's not a personal race, it's also for my country.
  "In the 100m, I beat myself. In the 200m, technically I ran to the best of my ability."
  When asked about the media's portrayal of him in the lead up to Beijing 2015, Gatlin said: "I go into shutdown mode. I don't worry about what the media has to say.
  "You guys do your job, sensationalise stories sometimes. My job is to compete and get to the line."
summary: Jamaica's Usain Bolt says he is "50-50" to compete at the 2017 World Championships in London because athletics is less enjoyable for him.