A normal person spends about a third of their lives sleeping, according to the National Institute of Health. Based on the average U.S. life expectancy of 78.21 years, that means you spend about 26 years of your life in bed.

We know we need sleep to retain memories and allow our muscles and organs to rest and recover. Scientists also recently discovered that sleep allows our brains to clean themselves of toxins.

Most people follow a monophasic sleep schedule, which involves seven to eight hours of continuous sleep every night.

Others, notably college students and the residents of many Latin American countries, follow a biphasic sleep schedule, involving five to six hours of sleep plus a 30- to 90-minute nap.

Throughout history, however, a bold few have attempted one of several outlandish polyphasic sleep schedules, bringing down sleep time to as little as two hours a day. Theoretically, these schedules could unlock an extra 20 years of being awake over the course of a lifetime.

Before we get into the types of polyphasic sleep schedules and the people who've tried them, Matt Bianchi, director of the sleep division at Massachusetts General Hospital, offers a warning: "Everyone is different. Some people drink caffeine and get a rush, while others don't. So one person might be fitted for polyphasic sleep, but someone else got sleepy and crashed their car."

If you want to experiment with polyphasic sleep schedules, we recommend not driving, operating heavy machinery, or making any important decisions until you determine how fewer hours of sleep affects you personally.

Polyphasic sleepers

Rumors credit the success of various famous thinkers, like Leonardo Da Vinci, Thomas Edison, and Nikola Tesla, to polyphasic sleep cycles. The first well-documented sleep dissident, however, was architect, inventor, and philosopher Buckminster Fuller.

Fuller experimented with polyphasic sleep throughout the mid-1900s and supposedly coined the Dymaxion sleep schedule, named for his brand name, combining the words dynamic, maximum, and tension. As the most drastic of the major schedules, the Dymaxion requires 30-minute naps every six hours, for a total of two hours of sleep per day. In his book, "BuckyWorks," J. Baldwin writes that Fuller achieved enormous success with his unusual sleeping habits, and his ability to fall asleep within 30 seconds wowed people. Fuller reportedly switched back to a monophasic schedule only after complaints from his wife.

Since Fuller, others have picked up on the idea of polyphasic sleep, too.

"Weening yourself off of sleep is not a new idea to the scientific community. Some people had success with it in the '70s and '80s," Bianchi said.

For example, in the '80s, Italian neurologist Claudio Stampi began to look into the benefits of polyphasic schedules. He noticed his fellow sailors adopting altered sleep without much difficulty and with many upsides. For one of Stampi's experiments he observed Francesco Jost, a Swiss artist, practicing polyphasic sleep for 49 days at his home. After the initial shock to his body, Jost's concentration and mood stayed relatively consistent, though he had trouble waking up at times. With minimal side effects in the short term, Jost squeezed five more hours out of his days. (The long-term impacts of these sleep schedules are unstudied.)

Today, amateurs on the Internet have undertaken their own studies of polyphasic sleep. Reportedly, Puredoxyk coined the Uberman schedule, which requires six naps of no longer than 30 minutes — typically at 2 p.m., 6 p.m., 10 p.m., 2 a.m., 6 a.m., and 10 a.m. In total, you get about three hours of sleep per day.

Personal development speaker Steve Pavlina adopted this sleep schedule for a brief time with impressive results. He listed boredom — not decreased concentration or sleepiness — as a major problem. In fact, he only reverted back to monophasic sleep to spend more time during the day with his wife and kids.

Puredoxyk supposedly created the Everyman schedule, as well.Everyman sleepers snooze for three hours, usually from 1 a.m. to 4 a.m., and then take three 20 minute naps, one at 9 a.m., 2 p.m., and 9 p.m. Puredoxyk said she preferred this version to the Uberman. She listed chiropractic benefits as well as breaking up the workday and having more time for hobbies, school, and her daughter. Read about her transition here.

The science

One theory supporting these alternate sleep schedules suggests that human evolution favored polyphasic sleep. A 2007 report from the Journal of Sleep Research found that the majority of animals sleep on polyphasic schedules, and they theorize humans probably wouldn't have evolved differently. Of course, the unique human brain may have different needs than the brains of other animals.

We know that most people follow monophasic sleep cycles, involving multiple cycles of around 90 minutes of non-rapid eye movement sleep followed by a brief period rapid eye movement (REM) sleep. We don't know, however, the exact purpose of these stages.

"I probably have a more cynical view than most, but I don't think that we know what part of sleep is the most restful," Bianchi said. Most likely, different phases of sleep have different restorative effects.

Lacking a good understanding of monophasic sleep, science struggles even more to understand polyphasic sleep. And some question whether polyphasic sleepers get enough REM sleep.

Polyphasic proponents often claim their altered sleep cycles trick the body into entering REM sleep more quickly. For example, during his home-based experiments Stampi found Jost's brain began entering REM sleep almost immediately during some of his naps while still satisfying the other sleep states. This immediate entry into REM sleep is called "repartitioning." When the body becomes sleep-deprived enough, it apparently adapts to achieve the necessary amount of rest, Stampi suggests.

Other polyphasic sleep proponents claim that REM sleep doesn't matter much anyway. Numerous studies show that people only suffer when deprived of sleep entirely, not just REM, according to The National Institute of Health. That suggests we might need non-REM sleep to survive, even though it could play a role in learning, memory, and emotional health.

Identifying the limited effects of sleep complicates the matter even further. For instance, many people with sleep apnea (poor nighttime breathing causing reduced sleep) don't feel sleepy during the day.

"If that doesn't predict how rested you feel, I don't know what does," Bianchi said.

Knowing the lifetime effects of polyphasic sleep also proves difficult.

"There could be non-measurable effects, chronic or long-term problems developing," he said.

Some of polyphasic sleepers' success could depend on their individual genetics. For example, the "sleepless elite," about 1% to 3% of the population, can survive on a few hours of sleep per night. A mutated gene, called the DEC2, allows these select sleepers to still get the rest they need. Conversely, some would claim that polyphasic sleep "tricks" your body into becoming part of this group.

According to a recent discovery, everyone used to sleep in two segments until the invention of electricity. People would wake in the middle of the night for an hour or so. They would probably still get 7 to 8 hours of sleep per night, though.

The professor Roger Ekirch has observed that older books such as "The Canterbury Tales" make reference to two different periods of sleep, Eric Barker has written. And after researchers conducted a study, they realized people, when devoid of artificial light, revert back to that schedule.

Regardless of the past, future sleep research may change the game again.

Understanding how "brain structure and function changes in the two different states [asleep and awake] suggests that we can start to think about how we can manipulate the two states," University of Rochester researcher Maiken Nedergaard told Business Insider in an email.

In other words, we probably won't need alternate sleep cycles but rather drugs that program the brain for ultimate sleep efficiency. In theory these could give us all of the benefits of limited sleep with none of the downsides.