John Cena can "operate" without sleep for 40 hours straight

Asked how he finds time to sleep, he told the Insight with Chris Van Vliet podcast: "I get rest. I used to - it's a thing from the Right Now [music] video where I have a sign that says 'Sleep is not mandatory'. I should cross out the 'not'.

"Sleep is mandatory, and I fashion my days around that.

"So, when we have, say, Budapest to Indy, Indy to Budapest, and I say I'm gonna sleep on the flight but I don't.

"And I know I need 12 hours on the backend. I know I can operate for, like, 36 straight, maybe 40."

Cena, 48, admitted he "gets blurry" around 18 hours in, and again at 28 hours.

But he added: "You ask people who work double shifts, medical professionals, this - a lot of them will say the same thing, you do get a second wind.

"But after that I need, like, three days - like, 70 hours of sleep. So, I will carve it out."

He admitted he tries to get 10 to 12 hours sleep in blocks to catch up on the sleep he's missed, and that means having a system in place with his wife Shay Shariatzadeh.

He explained: "I will get home from work, fall asleep in the car, stumble to a room, not even say hi to the wife, but we plan on this before.

"I call it asking for grace. 'We have a tough run come up, I need to ask for grace at these three points'.

"That means, 'normally it's in our values for me to check in on you in the morning and us to get together for at least 90 minutes, and talk about our day and what went on, what happened.

"'If nothing happened, what are you thinking about?' Just 90 minutes of us being there with each other.

"Asking for grace is like, zero minutes - survival and my well being, I just gotta get right back to me being good. Because me being it debt is doing nobody any favours.

"And she understands it!"