The incomparable Usain Bolt always challenges himself. Even though he is by far the best sprinter who has walked the earth, he has picked out a new target, smashing the 19-second barrier in the 200 metres.As monumental as that seems, the tall man from Trelawny is just the one to do it.He might have done it in 2010. After all, he had run world records of 19.30 and 19.19 seconds in the 2008 Olympic Games and the 2009 World Championships, respectively, and looked unstoppable. A 19.56-run solo at the Jamaica Invitational that year confirmed for me that the barrier was within reach.The numbers all seemed to add up. He stormed through a 44.2-second 4x400m relay anchor leg at the Gibson Relays and, on a rainy night in the Czech city of Ostrava, he stepped the second fastest time ever for 300 metres – 30.97 seconds.Injury and the desire to take it easy after three tough championship seasons intervened. He and guru Glen Mills wanted him healthy and fresh to defend his World and Olympic titles in 2011 and 2012. You know the rest. His victories in those seasons and this year at the World Championships have increased his lead over the rest of history’s best.For anyone to take his place, a new sprint king will need five world records, four of which need to be set in major finals, four individual Olympic gold medals and seven individual World Championship gold medals. That’s a tall order.Still at itHe could have chosen to rest on his laurels. You’ve seen football teams head for the corner flag to preserve a result. Not Bolt. He’s still on the attack.His choice to chase the 200 world mark is interesting. It seems almost to be an admission that the 100-metre record – his stupendous 9.58 from the 2009 World Championships – is safe. On top of that, the 200 is his favourite event.Perhaps he will run more early-season 400-metre races to build the endurance required to fight the fatigue in the last part of the 200. In the process, his longstanding 400m personal best of 45.28 seconds may fall. In fact, any serious effort would certainly put him under 45.I’ve always thought he is the only the athlete who could break Michael Johnson’s world record of 43.18 seconds. The wonderful American set that mark at age 31 in the 1999 World Championship final. Interestingly, though Bolt has always disavowed any interest in the 400m, he will be 31 in 2017, the year he has pinpointed as his last as an active athlete. That’s a flight of fancy.In the meantime, his 200 performances are so good that you almost see him breaking the record already. He has the only sub-20 by a junior – his 2004 Carifta time of 19.93 seconds and every major title on offer since 2008.Brilliant on the curve, his long strides carry him clear of every sprinter who has ever graced the track.Are you going to tell him that sub-19 is a barrier too far? I won’t.n Hubert Lawrence has made notes at track side since 1980.