Sleep is important. So says the slumbering eyes searching for the coffee pot and that artificial stimulation that will make us forget about the sleep we didn't have. In order for us to get the most out of that time we spend sleeping we should understand what is going on and why it is important.
According to the Sleep Architecture model sleep occurs in cycles. One sleep cycle is made up of five stages and lasts about 90 minutes. A typical night's sleep is comprised of five complete cycles. Stages 1-4 of a sleep cycle are non-rapid eye movement (NREM) or quiet sleep and stage 5 is rapid eye movement (REM).
Stage 1 is the time where you fall asleep and ends with light sleep. In stage 2 you become disengaged from your surroundings and your body temperature begins to fall. In stage 3 you fall deeper into sleep and the body begins its restorative functions by increasing blood flow to the muscles and releasing hormones to stimulate cell growth. Stage 4 finds you in deep sleep while your body continues to repair itself. Most of the high level functions of the brain (like speech) are shut down so more blood can be diverted to the body.
Stage 5 or REM is where you dream. During REM areas of the brain that handle emotions and memory are highly active while other cognitive functions are dormant. The muscles are also turned off and you are in a temporary paralytic state. A common nightmare can be contributed to this phenomenon. I myself, like countless others, had a recurring nightmare during my adolescence of someone standing over me while I slept and I was unable to move or even scream. In retrospect I now know that I was simply being woken up during a REM state and my mind and body were trying to correct it.
The sleep cycle moves you through these stages over and over again. The length of each stage changes throughout each cycle. The REM stage in the first cycle lasts about 10 minutes and lengthens each cycle there after lasting about an hour on the last cycle. Chemical and hormonal changes throughout the cycle's progression prepare you to be alert and rested upon completion of the cycles. If the cycles are interrupted the body and mind are not prepared to be awake and suffer accordingly. As illustrated by the REM nightmares.
There are a lot of theories as to why things happen the way they happen while we sleep. Do the muscles shut down to keep us from physically acting out our sleep or is it necessary for increased blood flow? We still don't know everything about sleeping but there are some things that are clear:
- Sleep is when the body does most of its repair work and growth.
- Growth, sex and fertility hormones are released during the sleep cycle.
- Other sleep cycle hormones help regulate your appetite.
- Sleep is vital to a healthy immune system.
- A regular sleep cycle supports (and is supported by) your circadian rhythm.
- Your body temperature falls when sleeping.
- The digestive system and metabolic rate slows down during sleep.
So how does sleep relate to ergonomics? Ergonomics is about the human-machine interface. The human need to be operating efficiently just like the machine does or else the system just doesn't work. So if you want to be at your best and enjoy your life the most then good sleep habits are vital. Now that we know what happens when we sleep we can be prepared and get the most out of our sleep cycles.