When Johnson began his quest for Olympic glory in 1993, his best time for the 110m high hurdles, one of the most technically demanding events on the programme, was 13.62 seconds. He won his Olympic title in 12.95 seconds. Three men share the credit for his big improvement. Curtis Fry, Johnson's coach at the University of North Carolina, and Dr Ralph Mann, Olympic 400m silver medallist from 1972, are the first two.
For the past 16 years, Mann has been working on computer bio-mechanic modelling with a grant from the US Olympic Committee, and various sponsors. Based in Orlando, Florida, Mann films the athletes he works with, then compares running/hurdling styles with the best in the world.
"We transfer the film on to computer, and animate it, then we compare it against the model that we have built from all the characteristics of the world's best hurdlers." This is where the third man in the equation comes in - "Stick-man".
"We run them side by side, so we're able to see what the athlete is doing wrong. Stick-man can do any speed you like, but it's technique we're looking for. Time on the ground is the key to everything in hurdling. And that can be precisely determined."
After the demonstrations, observers and advice, Johnson goes back to North Carolina and sets to work with his coach. Fry says: "We do lots of drills to change the placing of the foot ideally for the next lift- off. Allen's big problem was he was a total overstrider. He was sacrificing frequency for length. The good thing about Ralph Mann's work is that it's tailored to the individual."
It took Johnson a year to assimilate fully the recommended changes. But by 1995 he had: he won the world title in that year, and now he has the Olympic gold. Dr Mann feels that he can go a tenth of a second faster, which would considerably reduce Colin Jackson's world record of 12.91 seconds. But Mann insists that it is Johnson's team-mate Mark Crear, the Atlanta silver medallist, who is closest to Stick-man, and Florian Schwarthoff, the German bronze medallist, who is furthest away.
"Crear is almost perfect. He's 6ft tall, which is the optimum height for a hurdler. Schwarthoff is at least 6in too tall. I just don't know how he manages to squeeze the three strides in between the hurdles." Science obviously still has some way to go.