Mike Golding knows that he is tired when he pours boiling water directly into a full packet of coffee. “Then I know it's time to put myself to bed, because that is when you could do some real damage to the boat,” Golding said before starting the Vendée Globe this month. On day 18 of the three-month race, the 26 solo sailors left - out of the 30 that set off - will be dealing with serious sleep deprivation.

Vendée Globe sailors are at the cutting edge of “skilled sleeping”. Their ability to perform effectively alone in extreme conditions has helped to develop new standards of “catnapping” for everyone from astronauts to long-distance truckers in the past two decades. For about 90 days, they must try to survive on 5 hours' sleep in any 24-hour period, living in what is effectively a carbon-fibre drum. In the slamming conditions of the past few days, as the boats have been reaching south with strong easterlies, noise levels will have reached 120 decibels and skippers have been wearing sound-reducing headphones.

“Managing sleep properly is essential for a solo sailor not only for survival reasons, but more importantly as a way of winning the race,” Claudio Stampi, a sleep expert and director of the Chronobiology Research Institute in Boston, Massachusetts said. “It is a professional tool, you want to know about that in the way that you want to know about helming and trimming a sail.”

Stampi is the world's leading authority on sleep and sailing. He has worked with Golding and Dame Ellen MacArthur among others for the past decade, but developed his theories on polyphasic sleeping - or catnapping - from his own sailing experience. Stampi skippered a boat of doctors on La Barca Laboratorio, the research boat, in the 1981-82 Whitbread Round the World Race.

“I realised it [polyphasic sleeping] was a useful tool and not necessarily as difficult as it appeared,” Stampi said. “It was not so difficult to change the sleep pattern from a monophasic pattern [one long sleep] to a polyphasic pattern. That amazes me and everyone who practises polyphasic sleep.”

Stampi thinks this is because the model of one long sleep is relatively recent in evolutionary terms. He says that 85 per cent of mammals, for example, domestic cats and dogs, use polyphasic sleep. He believes that man in the hunter-gatherer society employed regular napping and only moved to one long sleep as society became more organised.

“I am not suggesting that polyphasic sleep is more efficient than monophasic sleep,” he said. “But when the system is under duress and you have only a certain amount of time, polyphasic sleep may become less costly.”

In the first week with the adrenalin-pumping and traditionally tough conditions in the Bay of Biscay, most were snatching snippets of sleep. The patterns of the sailors will be different now depending on whether they are night owls or early birds.

“It depends on your physiology. If are a night owl, like Mike Golding, you probably are not so well versed in napping - morning types are more natural nappers,” Stampi said. “Outside of those extreme periods, you will probably take a two-hour nap from 2am. Then a short nap in the late morning and then two 1-hour naps after lunch and another at a time to be determined by trial and error. Your target is a minimum of 5 hours a day.”

Golding, on Ecover 3, is among a leading group of nine who have mostly been within a hundred miles of each other from the start. They appear to have been conservative so far. “With 30 sailors, there are greater chances of having hotheads that will determine the pace of the race,” Stampi said. “It will be very difficult even for a more judicious sailor to manage his or her pace. I have seen those cases of sailors staying up for days, but I wouldn't recommend them at all. Ellen [MacArthur] can be demanding on herself, but I have her data and she never went even one day without some sleep.”