"It took me 15 minutes," he recalls, in his first interview since the illness. "I used to be the fastest person in the world at that distance. But I wasn't discouraged. I got back to my room and said to my wife, 'I will make a full recovery and I will make a full recovery faster than anyone has ever done it before'."
His will to succeed was as strong as it had been for any of his Olympic titles. There would only ever be one outcome.
It is now little over two months since the world was shocked by the news that Johnson had suffered a stroke.
Such events are unexpected by their very nature, but of all people to suffer such a fate, no one predicted it would be him.
More than 27 years since winning the first of a dozen global sprint titles, Johnson has always prided himself on being a model physical specimen.
Age has been no hindrance and he attempts to maintain a similar routine to that which made him the fastest man in the world: No smoking, no junk food, daily workouts. Which is exactly what he had been doing on that fateful day on August 31.
Everything had seemed normal. There were no red flags during an uneventful training session and even the weather was typical of a late summer's afternoon on America's West Coast, with clear, still skies.
Then, on exiting his home gym, the tingling began. There was no pain - in fact, there would be no great pain at any point - just an uncomfortable, unfamiliar sensation on the left side of his body. For a man who moved so smoothly on the track, he knew the coordination in his left foot was awry.
At first, he did what anyone would and searched online for an answer, but it was only after calling a colleague in medicine that his wife decided to drive him to hospital to be checked out. He did not leave the facility for six days.
The stroke diagnosis was fast, with doctors able to pinpoint a clot lodged in tiny blood vessels deep in the right side of his brain. Starved of blood, his lower left side was starting to shut down and his foot had turned totally numb. By the time he came out of an MRI scan, he could neither walk nor put any weight on his left side. The upper part of his body was also impaired, with limited coordination in his left arm and hand.
"The first question you have is will I be able to recover?" says Johnson. "Will I be able to walk again? Will I be able to stand again?
"The scariest part is the doctors saying there is no answer. Only time will tell. I was in good physical shape, so they said my chances were better, but they could not give me an answer. That is very scary.
"You start to think about loved ones - is my wife going to have to take care of me for the rest of my life? Am I going to be able to walk again? Am I going to be in a wheelchair? Am I going to be able to stand in the shower or go to the restroom alone? You're forced to think about what your life might be like if that worst-case scenario is reality."
There were other emotions as well. "Definitely anger," he says. "For many people who have suffered a stroke, it comes from heart issues or cardiovascular issues - but they weren't able to find any of that with me.
"I don't have a history of heart disease, I don't smoke, I was working out when this happened, I don't eat junk food. So, initially I was very angry, thinking I'd done all of the right things and made all of the sacrifices, so why is this happening to me? Here I am, 50-years-old and I suffered a stroke. What gives?
"I was very upset for a while, but the sooner I got into physical therapy and started to work on getting better, I knew that would be better for my mind."
It was then that his fight began. Confronted with the task of teaching himself how to walk again from scratch, the single-minded determination required during decades spent honing his body to the exploits of an elite sprinter proved vital.
Within three days, he was standing at the end of the 200m hospital corridor preparing for the walk that would convince him everything would eventually be fine.
"It was clear to me then that the only thing standing between me and a full recovery was my ability to focus and work through the pain," he says. "I just needed to get into training mode and dedicate myself to that. I just had to get back into the same mindset I did while I was competing and training for the Olympics."
It worked. His walking aid was ditched after a matter of days, he returned home from hospital within the week and, exactly a fortnight after the stroke struck, he celebrated his 51st birthday with a workout on his terrace in the California sun.
Incredibly, he says he is now physically fully recovered. Aside from taking daily blood-thinning and cholesterol-lowering medication, the illness should have no impact on his life in the future, although, even after countless tests and procedures, its cause will almost certainly never be found.
Instead, like the ferocious competitor that he is, he is determined to consign the incident to the past.
"I have gotten comfortable with the idea that we're never really going to have an answer," he says. "I think 30 per cent of strokes don't have an absolute answer as to what caused it. In all likelihood, it's an anomaly and one of those things.
"I've had to come to the acceptance that instead of asking, 'why me?' ask, 'why not me?' It happens to people and it happened to me. I don't think we will ever know why."
