This little bit of science may explain why you're not feeling rested and refreshed when you wake up, even if you're getting 8 hours!
It has to do with the phases of sleep. You probably know that the brain and body go through different phases throughout the night. The phase known as REM (Rapid Eye Movement) is the most famous and well known because it's most associated with dreaming.
There are actually three phases of sleep that are "non-REM". The third phase of these three is called "Non-REM3". The quality of this phase of sleep is most associated with the body being able to feel refreshed and rested upon waking. This is the phase when the muscles will be the most relaxed that they will ever be during sleep.
This is where things get interesting. The relaxation of the muscles during Non-REM3 seems to be crucial to the ability of the body to be refreshed and rested. If something inhibits the full relaxation of the muscles, like a magnesium deficiency, then the body wont feel the full benefit that this phase of sleep has to offer.
With an estimated 50% of the population deficient in the essential mineral magnesium, this may help explain why so many people are walking around groggy, tired and feeling like a foggy-headed zombie.
The use of a magnesium supplement like Magnesium to the Rescue has long been used to help get a better night of sleep, and now we may know more about why it helps so much.