(CNN) -- Bolton Wanderers midfielder Fabrice Muamba did not respond to 15 defibrillator shocks and was in effect dead for 78 minutes before his heart started beating again, doctors who treated him have revealed.
The 23-year-old has improved significantly since suffering a cardiac arrest during an English FA Cup match last Saturday but is still in intensive care with his condition described as serious.
Muamba is responding appropriately to questions though, speaking in both French and English, and has been joking with some of his many visitors.
Bolton's club doctor, Jonathan Tobin, spoke for the first time on Wednesday, talking reporters through the severity of Muamba's collapse and the frantic efforts made to save his life.
Tobin said he and the other paramedics who rushed onto the field treated Muamba for a total of 48 minutes on the pitch and en route to London's Chest Hospital, but it took a further 30 minutes to restart the midfielder's heart.
"In effect he was dead in that time," Dr. Tobin said. "Fabrice was in a type of cardiac arrest where the heart is showing lots of electrical activity but no muscular activity.
"It's something that often responds to drugs and shocks. Now heaven knows why, but Fabrice had, in total, 15 shocks. He had a further 12 shocks in the ambulance."
Muamba's plight stunned players and supporters as the Congo-born star dropped to the floor with no-one near him just before halftime in the match.
And Tobin explained the exasperation he felt as he sprinted onto the turf with the other medics on hand at the stadium, to try to save Muamba's life with 40,000 people looking on.
"I can't begin to explain the pressure that was there," he said. "This isn't somebody that's gone down in the street or been brought into accident and emergency.
"This is somebody that I know, I know his family. This is somebody I consider a friend. This is somebody I joke with on a daily basis. As I was running onto the pitch I was thinking 'Oh my God, it's Fabrice'."
The desperate effort to save Muamba was assisted by an off-duty cardiologist, who was in the stadium watching the game as a fan and was allowed onto the pitch.
Dr. Andrew Deaner suggested Muamba be transferred to the London Chest Hospital, where he works, and administered vital drugs to the player in the ambulance.
He says the fact Muamba is responding appropriately to questions and is able to make jokes within five days of suffering such major heart trauma is nothing short of astonishing.
"If you're going to use the term miraculous, I guess it could be used here," he said. Deaner also revealed he had been in to see Muamba a few hours after he woke up.
"I whispered into his ear 'What's your name?'," he explained. When Muamba said his name Deaner continued: "I said 'I understand you're a very good footballer'. And he said 'I try.'
"He's made a remarkable recovery so far. We don't want to get ahead of ourselves. As things stand, I think his life is not in danger at this time. His neurological function is looking very good but it is early days."
Meanwhile, Bolton will be back in action on Saturday after Muamba's family gave their blessing for the club to face rivals Blackburn Rovers in the English Premier League. Bolton's proposed league match with Aston Villa, scheduled for Tuesday, was postponed.
"We spoke together with the players as a group this morning and I talked with Fabrice's family last night," Bolton manager Owen Coyle told the club's website.
"Fabrice's father Marcel and his fiancée Shauna were keen that we fulfill our fixtures. Once the players knew this, there was no doubt in our minds that we would play the matches."
The FA Cup quarterfinal with Tottenham that was abandoned in the wake of Muamba's collapse, will be replayed on March 27 at White Hart Lane.