Athletics great Michael Johnson is coming to terms with the fact he may never know what caused him to suffer a stroke in 2018.
Johnson, a four-time Olympic gold medallist and an eight-time world champion, took ill in September despite continuing to live an athlete's life in retirement.
The 51-year-old lost mobility in the aftermath of the stroke but says he has now returned to his former regime, albeit without certainty he will not suffer a relapse.
"We've sort of concluded that we'll probably never find that cause," Johnson told BBC Sport.
"It's something I've had to come to terms with. If I knew what the cause was, I could potentially do something about it and feel much better knowing that this is what caused it and now I have eliminated that potential issue. Unfortunately, I don't have that luxury.
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"Obviously that could create a little bit of fear, that I was doing all the right things before the stroke and now am doing all the right things again, even more. Yet it could happen again."
Johnson admitted that suffering a stroke while still in peak physical condition had been hard to understand.
However, once his anger passed, he decided to be positive.
"Having been doing all the right things like training every day and keeping myself in good shape while other people aren't, and they are fine and I am laying in a hospital bed having suffered a stroke, obviously you are going to be angry about that," he said.
"Telling yourself not to be angry is only going to make yourself more angry. You have to replace that with something and I was pushing my doctors to let me get into physical therapy as soon as possible."
