Four-time Olympic champion Michael Johnson is recovering well after suffering a "mini stroke" last week.
The former sprinter, who previously held the 200 and 400 metres world record, revealed on Twitter on Saturday that he had suffered a transient ischemic attack.
However, Johnson added that he is making "great progress" and took the opportunity to raise stroke awareness.
"Last week, I rather surprisingly suffered what's known as a Transient Ischemic Attack or mini stroke," the American posted on his social media page.
"The good news is I'm back at home with my family, cleared of any heart issues and have already made great progress on my road to a full recovery.
Johnson's initial post received messages of support from fellow athletics stars Jessica Ennis-Hill, Colin Jackson and Denise Lewis.