World Championships 2015: Usain Bolt 'sad' at doping focus

Defending 100m and 200m champion Usain Bolt is "sad" that questions about doping in athletics are taking centre stage before the World Championships in Beijing.

The Jamaican world record holder says he is running for himself and that the responsibility for clean sport is "not only on me".

Bolt is expected to face American Justin Gatlin - the world's fastest man this season - in Sunday's 100m final, with his rival having served two drugs bans.

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