Circadian Rhythms

To be filed under "Stuff We All Should Know"

We all have a built in biological clock. It does more than just make us feel crappy after we "spring forward" in early March. Among other things it controls:

  • wakefulness
  • sleep
  • metabolism
  • HR
  • BP
  • body temp
  • etc.

Our daily patterns are set to a Circadian Rythm which cycles every 24 hrs. If we disrupt this cycle by just a smidge, like 1-3 hours, we'll feel it. Some of us feel it immediately. Others of us get a lag of several days, or even weeks.

Throwing your body out of it's normal rhythmic patterns is known to cause: 

  • hot flashes
  • chills
  • stomach aches
  • grogginess
  • irritability
  • and sudden bursts of energy followed by extreme fatigue.

We know the part of your brain where Circadian Rhythms live. It's in your supraschiasmatic nucleus (SCN). That's in the hypothalamus. The hypothalamus seems to be fairly important to your health in that it regulates stuff like, body temperature, fluids/electrolytes, hunger, and hormone production. I'm not saying you couldn't get healthy without help from the hypothalamus, but if you were to fry the damn thing by screwing up your Circadian Rhythms hard and often - you might struggle a bit. 

The other thing we know is your SCN is connected to the retina of your eye. If it is dark, the SCN tells your body to secrete melatonin and make you peacefully sleepy. If it's light, the SCN inhibits melatonin production. Hint: if you are having trouble sleeping please ponder on the "darkness" thing you just learned. 

In the winter (assuming you live far from the equator), your SCN has developed a strange way of adapting to the longer periods of darkness. It produces melatonin in 2 stages. The first stage happens within a couple hours of sundown. Ever notice you get sleepy earlier in the winter? The other happens around 4 am. In the middle of all of that, there is a natural period of restful wakefulness. But there is a problem. In the developed world we don't go to bed earlier in the winter like our ancestors did. Instead of following our natural rhythms, most of us are just barely turning in right around our period of "restful wakefulness." This makes it harder to go to sleep in the winter. Ever notice?

Not getting enough sleep, or enough of the right kinds of sleep throws us out of our natural Circadian Rhythm. This can be one of the reasons why (for some of us) our fitness goes to hell in the winter. It is likely also a contributing factor to weight gain, irritability (who doesn't get a little pissy about gaining weight?) and general lethargy. It can also be why most of us get sick in the deep winter. 

Therefore one of the most important keys to obtaining good health & fitness seems to be: don't let your Circadian Rhythms get too far out of whack. If they do get out, get back back on track - ASAP. 

A couple more things to know: 

  1. Circadian is Latin for "about one day." 
  2. We sleep best when body temp is lowest. 
  3. When your daily Circadian Rhythms peak, you are stronger and have a higher tolerance for pain. So maybe wait and try to only allow yourself to have catastrophic accidents later in the afternoon?