Jake Coleman, 27, collapsed after completing the 13.1 mile course on Sunday (March 24).
He went into cardiac arrest and required resuscitation from paramedics who arrived on the scene within seconds.
He was taken by ambulance to Sea Road, St Leonards, where he was airlifted to Eastbourne District General Hospital.
Race director Eric Hardwick said: “We had a runner collapse after finish on Sunday and his heart stopped.
“Fortunately, we have fantastic medical cover for the event and he was attended to within seconds, and a defibrillator used to bring him back.
“Once stable, he was taken by ambulance to the beach at Cinque Ports Way where he was picked up by the air ambulance and taken to Eastbourne Hospital, where he was well looked after but in a critical but stable condition.”
On Monday, Jake’s mother told Eric her son was sitting up and talking.
She told Eric she was pleased with his progress and the way he had been looked after so promptly.
Eric added: “This was Jake’s second Hastings Half.
“In some ways it was a good place to have a cardiac arrest, if there is ever one, because the medical team were standing by.
“It also shows how important defibrillators are in this situation.”