British swimmer Michael Jamieson has revealed that doctors had to restart his heart on Wednesday morning.
The 25-year-old, who won a silver medal in the 200m breaststroke at the London Olympics in 2012, was treated at Royal United Hospital in Bath.
"Long week! My heart was restarted on Wednesday AM, pushing bit too hard at training on Tuesday haha," he wrote on Twitter. "Docs & nursing staff at RUH/EIS have been amazing.
"I'm back home & cleared to train! Specialist said he's only seen this 3 times, all Olympic medallists - pretty cool!
"Not really sure the reasons behind it happening but I went into an irregular beat after reaching 203 heart rate in a session (max is 193)."
Jamieson finished second in the 200m breaststroke at the Beijing World Cup earlier this month.