Gloucester's Adventureman, Jamie McDonald, is recovering in hospital after breaking a world record.
Seven days running 524 miles (842km) on a treadmill has taken its toll. Jamie was admitted to hospital after a home visit by a doctor.
The doctor was "disturbed" with results which showed his red blood cell count drop by a half and muscle enzyme levels elevated by more than a third.
The-32-year-old is being treated at Gloucester Royal Hospital and is waiting for further tests, including a CT scan, to ensure a full recovery.
A note on his Adventureman Facebook page says: "Thank you for all of the messages asking after him, and we will update when he's ready to leave - we keep telling him that it's OK to be taking it easy given he's just done something literally no other human being in history ever has (!) - but he's keen to be back on his feet soon."