The Barclays Premier League star's heart stopped beating naturally for 78 minutes after he collapsed in a heap during Bolton's FA Cup quarter-final at Tottenham on March 17. He was unconscious for three days despite feeling "particularly fit" before the incident, and awoke to find he could only manage a handful of paces when he was helped to his feet.
He told The Sun: "I couldn't believe how wrecked I felt. I only managed about five paces from my bed, but felt like I'd just run the London marathon."
He added: "It was a shock feeling like that because I've trained hard all my adult life and like to think I'm in very good shape."
The devout Christian, 24, stunned doctors after making a miraculous recovery and was fit enough to walk out of hospital just a month after the ordeal. However, it is not known if he will play professional football again.
Reliving his first steps, he added: "Once I was on my feet for the first time I felt like a toddler again - like my three-year-old son Joshua. I could barely put one foot in front of the other and had to be carried back to my bed - but it was a start."
Muamba was discharged from the the London Chest Hospital last Monday - almost a month to the day after he suffered the cardiac arrest.
He has been building his fitness by taking short walks with his fiancee Shauna Magunday.
"A few months ago I would think nothing of running miles, but now I'm tired after a 20-minute walk around the block," he said.
"But now I'm making progress. It's too early to say whether I'll play football professionally again but I have great faith in God and I have hope, so who knows? If I can come back from the dead then perhaps I can achieve anything."