After a stupendous world record of 19.32sec had secured the 28-year-old Texan a place in history as the first man to win the Olympic 200 and 400 metres double, he was asked to explain the unexplainable: what did it feel like to be the fastest man in the world? He did his best.
"I knew coming off the kerb," he said. "You can always tell when you make the transition from the kerb to the straight. I felt at that point that I was running faster than I'd ever run before in my life. As far as describing what that's like... well, it's an incredible thrill."
He paused, searching for a better means of expression. "My dad bought me a go-kart when I was a kid... and did I ever make that thing go fast - down the hill, whoosh. That's the only thing I can think of that compares. So if you want to know how it feels, go get you a go-kart, find a hill..."
At which point the bronze medallist, Ato Boldon, chipped in: "That's my next training method." In the tumult that greeted Johnson's victory, Boldon, an obsessive student of sprinting history, had bowed to him with arms outstretched, as if to say: "We are not worthy."
It was a performance which left the Texan's opponents almost speechless. Frankie Fredericks, who had ended Johnson's unbeaten sequence of 38 races by defeating him at this distance in Oslo last month, ran the race of his life to record 19.68, just 0.02sec outside the world record Johnson had set on the same track two months earlier at the US Olympic trials.
Fredericks ended up five metres adrift, in what looked more like the finish to one of Johnson's 400m races. "I thought when he ran 19.66 it was incredible," Fredericks said. "To run 19.32... I don't know what to say."
The obvious point of comparison is with Bob Beamon, who put the long jump world record out of reach for 23 years in winning the 1968 Olympic title. Johnson's advance - ramrod-backed, with pattering steps - is just as enormous. No one has ever reduced the 200m record by such a margin. But there is one man who might better the achievement in the next few years - and that man is Michael Johnson.
You could almost see Boldon and Fredericks sinking further into their chairs either side of him as he described how his race could have been better, saying that a stumble out of the blocks had cost fractions of a second.
"I didn't use my arms like my coach was telling me to do in practice," he said. "That's what happens when you don't do what your coach tells you." There seemed not a trace of irony in his remark.
Johnson does have a wry sense of humour which is becoming increasingly obvious as he works to overcome his innate shyness. But he is a man obsessed with detail.
He is so tidy that his sister, Deirdre, once complained that his condominium in Dallas "looked like no one ever lived there". He is said to keep his passport in the P folder of an impeccably maintained filing cabinet. His kit is always meticulously laid out before races, including pre-race and post-race snacks.
It was entirely in character that he should shy away from a question asking him if he regarded himself as "The Man" on track. "That's something that's left up to the fans' opinion," he said. "I just concentrate on the things that I can control and look for specific criteria."
What Johnson has found hard to control is the stress which his double plan has imposed. The schedule was altered to ease his path. He took to the track in gold shoes. Self-imposed they may have been, but these stresses were enormous.
"Pressure," he said. "There's never been this much pressure on me in my entire life. Every day when I picked up newspapers and magazines, there was always something about this double. Every time I went out into the streets, people would mention it.
"People called me to take the pressure off," he said, adding with a slow grin, "and that was just adding more pressure. That's what it's been like for the last six months. I was afraid out there that maybe I wouldn't be able to get the medal. It makes you get nervous. But that's OK. I like to be nervous. I ran like I was nervous."
His reversal of fortune at the last Olympics, when his position as 200m favourite was crucially undermined by food poisoning, has served, not surprisingly, as a big motivating factor.
"Today is, for me, a big relief," he said. "It sums up what my career is all about. After winning the 400m I felt like there was a plan for me after all the setbacks I had had. All I could do was to go out and perform to the best of my ability and leave the rest to God."
How, he was asked, had he found the strength to complete eight races successfully on a track so hard that even the sprinters were complaining about its attritional effects?
"It is partly mental strength, and partly the programme that my coach, Clyde Hart, has made up. We welcome multiple rounds. That's the way we train.
"A lot of people paid a lot of money to see this, but if they saw me in practice, that's where they get their money's worth, because we are going at it."
The super-human effort did tell, however, with Johnson pulling out of today's 4x400 relay final, citing a tight hamstring.
There was one other significant statistic attached to his performance. The victory margin of 0.36sec was the biggest in the men's Olympic 200m event since 1936, when 0.4sec separated the second-placed Mack Robinson of the United States from the champion - Jesse Owens.
Shortly after the US Olympic trials, Johnson received a letter from Owens's widow, Ruth, congratulating him upon his achievements on the track, and the way he conducted himself off it.
"It was the greatest honour I have ever received in my life," Johnson said. He had brought the letter along with him on every one of his six visits to the Olympic stadium. And in the end, his greatest honour was honoured.