Friday, December 29, 2006

The Inner Sleep Clock

The Underlying System that Governs Our Sleep and Energy
Have you ever wondered? How some people can wake up at precisely the same
time every morning without an alarm clock? Perhaps you've had this happen to
yourself a number of times, or maybe it happens already.
Also, why is it that we have alarm clocks to tell us when to wake up, but very few
people have alarm clocks to tell them when to go to sleep? I know, it's kind of a
stupid question, but there's actually a reason behind it, and you're about to find out
There is an underlying mechanism, called the sleep clock, which consists of a
number of variables in your body that tell it when to feel tired, and when to feel
awake. It also controls how deep you sleep, and how long you sleep.
Refer to the chart below:
Neat eh? But what does it mean? Ha...
Circadian rhythm
The first, and most important part of your sleep clock is your body temperature
rhythm. It’s also known as a circadian rhythm.
Contrary to what most of us are taught in grade 5 science class, our body
temperature doesn't stay at a constant 98.6º Fahrenheit (37º Celsius). Our body
temperature actually has a specific rhythm to it. It rises and drops as the hours of the
day progress. The difference in body temperature is about 3º Fahrenheit (2º Celsius)
This periodic rise and drop in body temperature tells our mind when to feel tired and
when to feel more awake. As body temperature rises, we tend to feel more awake
and our brain waves are usually higher. As body temperature drops, we tend to feel
more lethargic, tired, and lazy - this is a big cue for our minds to lower brain waves
and enter Stage 1 sleep.
As you look at the graph again, you might notice that there is a slight “drop” of body
temperature during the mid afternoon. This is a usual mid-afternoon body
temperature slump. You may have noticed, at some point in your life, that you
usually feel an urge to sleep or take a nap during the afternoon. This is completely
natural, and sometimes the pressure to sleep during the afternoon is as strong as
the pressure at night! (Although most of us chose a drug of choice, such as caffeine,
to combat this body slump).
Because of the demands our society puts on us, such as work, children, and social
life, most of us can't sleep at this time. As we'll explore later on, nature actually
intended for us to have a nap at this time - we'll talk about the science of naps in
Generally, body temperature begins to rise in the early morning hours, drops
sometime during the afternoon, then begins to rise until the early hours of the
evening. It's at this time that we have “peak performance” body temperature, most
people are most active during the early evening hours, this is where body
temperature is the highest. Afterwards, body temperature drops and reaches its
lowest point at around 4 am.
If your body temperature rhythm is too flat (doesn't rise or drop low enough), or if it's
messed up in any other way, chances are you will experience sleep difficulties. It will
be difficult for you to sleep deeply. We'll explore all the causes of that later on in this
It's because of the body temperature rhythm that most of us feel sleepy, at precisely
the same time every night. It's also why some people can wake up without an alarm
clock at precisely the same time every morning.
Usually, your body temperature rhythm will follow the same pattern regardless of
when you fall asleep. For instance if you've been waking up at 7 AM all your life, this
means your body temperature begins to rise at this time. It won't matter if you fall
asleep at 11 PM, 12 AM, or 1 AM, your body temperature will rise at 7 AM, and you
will feel sleepy at the same time you always did the next day. Unless you take the
proper actions to optimize your body temperature, it will usually return to the same
pattern. This is the main focus of this book.
This is the primary reason why jet lag happens. When you travel really quickly
across several time zones, your body may be in a different time zone, but your
temperature rhythm is still following the pattern it did before!
So if you normally live in Florida, and you take a flight to California; if it's 8 PM in
California, your body will still think it's 11 PM, based on your temperature rhythm. As
you see, your temperature rhythm really acts as an internal “clock”.
Your body temperature rhythm can adjust to a new time zone, or a new sleeping
pattern, and this may take from a few days to up to several weeks! This is why
trans-continental jet lag is so severe for some people.
Your body temperature rhythm is perhaps the most important concept to grasp about
your inner sleep clock. It has a huge impact on how you sleep, and how you function
during the day.
So what affects your body temperature rhythm? And how could someone possibly
“damage” their body temperature rhythm?
The second important element of your sleep clock is your melatonin hormone level,
and your exposure to natural sunlight.
Melatonin and Sunlight
Have you ever wondered why human beings sleep at night? Did someone just make
the decision one day: “Okay Guys! From now on we're all going to go to sleep when
the big light in the sky turns off!”
That could possibly be it! But there's actually a system inside of us that uses light
and darkness to control certain sleep hormone levels.
Melatonin is a hormone synthesized in the pineal gland and, to a lesser extent, in
the retina. Melatonin is responsible for putting you to sleep and restoring physical
energy while we sleep. If your melatonin levels are high, you will experience feelings
of drowsiness, loss of energy, etc.
Melatonin is released when we're exposed to darkness. The instant sunlight stops
entering our eyes, our melatonin hormone level begins to rise. Your melatonin levels
are EXTREMELY dependant on the amount of natural sunlight that enters your eyes
during the day!
Higher exposure to sunlight delays the body temperature drop, and lets you stay
awake and alert longer. Poor exposure to sunlight will promote a quick temperature
drop and make you feel sleepy, tired, and out of balance. You will most likely
experience the pressure to sleep very early in the day, or the pressure to sleep will
be very minimal which might cause insomnia and poor quality sleep.
Because melatonin is released when we're exposed to darkness, it is also
sometimes called the vampire hormone.
We'll explore exactly how important sunlight is in a later part of this book. However
it's important to understand that getting proper sunlight isn't an “optional” part of this
program, it's a MUST, as it is the main way our body adjusts our body temperature
Activity Level
The amount of movement and cardiovascular exercise you get during the night has a
huge impact on your body temperature rhythm. Any movement or exercise promotes
a quick rise in temperature which can be very beneficial to the sleep system.
Exercise creates a higher “peak” point of body temperature during the day, which will
increase your energy levels far beyond anything else. Exercise delays the body
temperature drop at the end of the day, allowing you to stay awake and alert longer.
Finally, exercise will make the drop of body temperature at the end of the day more
drastic and allow your body temperature to stay lower for a longer amount of time;
this will promote much deeper sleep.
Prior Wakefulness
Obviously the amount of time you're awake has a direct effect on all three factors
above. Your activity levels contribute a lot to your temperature variations. Also, the
longer you're awake obviously means you get more potential for sunlight entry into
your eyes, which has a direct effect on your melatonin level.
If you're currently sleeping 8 or 9 hours and you feel tired during the day this could
actually be a sign that you need LESS sleep. You're sleeping too much and you
need to increase your prior wakefulness to create deeper sleep and a more balanced
body temperature rhythm.
The four factors up above control how long you sleep, and how deep your
sleep is. To summarize, the factors that affect your sleep the most.
1) The body temperature rhythm.
2) Natural sunlight entering your eyes, as it has a direct effect on your melatonin
Understanding how the body temperature rhythm affects your sleep is the key to
optimizing your sleep. The body temperature rhythm is really what makes the sleep
clock a... “Clock”.
Usually, your body temperature follows the same pattern regardless of when you go
to sleep. For instance, if you routinely get up at 8 am every day, this means your
body temperature begins to rise at 8 am. If you feel drowsy for the next 3 hours, this
means your body temperature is slowly rising during this time, and hasn't reached it's
peak point. For most people the optimum peak point of body temperature is at
around 6 PM to 7 PM, this is when we are naturally most active and have the most
energy. Study the previous graph if you still aren't clear about how the body
temperature rhythm flows.
If all of a sudden you revert to waking up at 6 AM instead of 8 AM, this doesn't mean
that your body temperature will begin to rise at 6 AM, it will remain low and begin to
rise at 8 AM like it usually did, and possibly making you feel drowsy for 5 hours
instead of 3. Unless you expose yourself to high-intensity light, as we'll explore soon.
This is why it is so hard to force yourself to wake up early, and why the popular belief
persists that waking up earlier than usual is painful!
This natural “clock” is also why some people do not need an alarm clock to wake up
at PRECISELY the same time every day. This isn't a mysterious psychic force they
have; their body temperature simply rises at precisely the same time everyday.
In the next section we'll examine all the details of optimizing your sleep clock.
Section Summary
Take this short quiz to better learn and remember what you've just read.
1. What best describes deep sleep?
a. Super high brain waves, twitching muscles and rapid eye movement.
b. A type of human hibernation, we can use deep sleep to sleep past really cold
c. Low brain waves, respiration, heart rate, and blood pressure. Dilated blood
vessels to allow blood to the muscles.
2. What is the sleep clock?
a. A system inside your body that counts the time until your inevitable death.
b. A system that measures blood pressure to determine when it's time to sleep and
when it's time to be awake and alert.
c. A system that measures light intensity and body temperature to determine when to
sleep, and how physically recharging your sleep is.
3. We sleep during the night because...
a. We're all vampires except we're not aware of it because we enter a different state
of consciousness while we're out partying with Dracula.
b. It just seems like a good idea to sleep at night so we all do it.
c. Melatonin is produced during the day which prevents us from sleeping.
d. Melatonin is produced when we're exposed to darkness, which causes us to feel
sleepy and our brain waves to lower.
4. Our immune system turns on to fight diseases in what sleep stage?
a. Stage 1
b. Deep Sleep (stage 3 & 4)
c. REM sleep
d. When we're sleep walking or snoring.

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