The questions continue following Usain Bolt's world record winning performance at the World Athletics Championships in Berlin yesterday - how low can the 100 metre time go?
Bolt lowered his own world mark to 9.58 seconds.
Many have suggested that the Jamaican star is far from technically perfect and that it takes a good three years to master the distance.
The former world 200 metre Alton Bolton believes Bolt still has a lot to learn.
Bolton says there were 10 things he could get Bolt to improve on but he thinks the fastest man alive may yet break the 9.5 second barrier - although it will take minor, incremental changes over a much longer period than his massive improvement of 1.1 seconds since last year's Beijing Olympics.
Bolt is still to run the 200 metres at the world championships.
