Former England midfielder Carlton Palmer said he was being kept in hospital for further tests following a "suspected small heart attack" during the Sheffield Half Marathon on Sunday.
Palmer - who had spells at West Brom, Sheffield Wednesday and Leeds during a lengthy playing career, winning 18 international caps - was admitted overnight with observations continuing.
The 57-year-old, who later had managerial stints at Stockport and Mansfield, underwent a lengthy operation in 2016 for a heart condition which involved surgery to widen arteries.
Palmer wrote on Twitter that his "heart played up again in the first mile" of Sunday's race, which resulted in him going to hospital.
"Thank you so much for all the lovely messages I have being kept in hospital with a suspected small heart attack," Palmer said in an updated Twitter post on Monday.
"They want to find out what has caused this problem so tests are ongoing."
Palmer made three appearances for short-lived League Of Ireland club, Dublin City, in 2004.
