In the early 2000s, a concept called the “Uberman Sleep Schedule” circulated on the internet, suggesting that individuals could train themselves to sleep only two hours a day by taking 20-minute naps every four hours. The underlying idea was that the majority of the benefits from sleep come from REM sleep, which lasts about 20 minutes every two hours. The payoff for adhering to this regimen would be significant additional waking hours over a lifetime. However, the method required intense self-discipline and sleep deprivation during the initial adjustment phase.
  

Key Points: 

1. The “Uberman Sleep Schedule” claimed that by taking 20-minute naps every four hours, individuals could reduce their total daily sleep to two hours.
2. This concept is based on the idea that the most restorative part of sleep, REM sleep, only constitutes about 20 minutes in every two-hour sleep cycle.
3. Adhering to this sleep schedule could theoretically provide an individual with over a decade of extra waking hours over their lifetime.
4. The initial adjustment to this schedule requires intense sleep deprivation and extreme discipline, with no allowances for deviations like oversleeping.
5. Despite its purported benefits, adapting to the “Uberman Sleep Schedule” proved to be a challenging and potentially unhealthy endeavor for many, including the author.

Source: https://markmanson.net/self-discipline