Sprinting legend Michael Johnson is recovering at home in America after suffering a medical scare.
The 50-year-old said on social media that he had suffered a Transient Ischemic Attack (TIA), also called a 'mini-stroke', last week.
According to the Mayo Clinic, symptoms of a TIA are similar to those of a stroke, but usually go away after about an hour.
The four-time Olympic champion, who held the 400m world record until Wayde van Niekerk broke it at Rio 2016, currently works as a TV analyst.
But he says being a former athlete is helping with his recovery.
"I'm no stranger to a good exercise plan and have thrown myself into it with my usual focus and determination," he tweeted.
Johnson won 4×400m relay gold at Barcelona 1992 before completing an unprecedented 200m–400m double at Atlanta 1996.
He retained his 400m title at Sydney 2000, and also won eight world titles during his career.