Do You See the Light?

As you may have heard, winter is coming.  This transition always hits me the hardest when daylight savings time ends.  And it’s not just me.  There’s an increased incidence of depression when we turn our clocks back an hour (1). To understand why this is (and what we can do about it), we’ve first got to learn a little physiology.

Nearly all of your body’s tissues, organs, and cells have an “internal clock”.  This internal clock allows your different organs to operate at their best when needed.  For example, your ability to regulate blood sugar levels is greater in the morning compared to the evening (2).  This also holds true for athletic performance with peak performance typically occurring in the early evening (3). 

While we have all accepted that there are 24 hours in a day, our internal clocks have not.  Everyone has an internal clock that has chosen how long it wants the day to be.  Some folks have internal clocks that want to operate on a day that’s shorter than 24 hours and others have an internal clock that’s slightly longer.  This difference in internal clock length is thought to determine whether you are a morning (shorter clock) or night (longer clock) person (4).

Your internal clock would work without any outside stimulus, but there are things that can influence it (5).   The big influencer (and the way we’re tying this all together with daylight savings time…) is light. Abrupt changes to light exposure, as is the case with traveling across time zones or changes following day light savings time, can cause disruption to your internal clock. 

Because nearly all of your cells have an internal clock that helps them function properly, disruption to your internal clock influences most everything.  A plethora of consequences have been shown with both mental and physical health (6).  These negative consequences include depression and weight gain and other factors which contribute to athletic performance. 

So now you have a bunch of fun facts for your next cocktail party.  But that’s not why you are reading this.  You want to get faster and stronger.  How can we use this science to improve performance?  Well, what we can do is use light exposure to our advantage. 

One way to improve performance is to increase alertness.  Dark mornings in the winter can make it hard to get out of bed.  But turning on the lights can help you wake up. For folks who work-out in the morning, get those lights turned on early.  In addition, if you’re like me and are restricted to riding the trainer early in the garage, set up some lights to brighten up your space and help you get through those intervals. 

Increasing alertness is not the only way to improve performance. As you know, rest and recovery is just as important.  So, if light helps you wake up and get going in the mornings, then we want to do the opposite at night.  Light exposure reduces melatonin secretion which makes you less sleepy (7).  Therefore, to make it easier to fall asleep, turn down the lights and stay away from computer screens. 

Now let’s put it all together and look at a case study. A former roommate of mine was traveling to Israel and wanted to limit jet lag so that he could hit the ground running as soon as he got there. In the late afternoons/evenings before his flight, he reduced his light exposure by turning the lights low and wearing sunglasses. In the mornings, he’d get up real early and turn the lights on to help him wake up.  Thanks to these pre-travel changes in light exposure, when he arrived in Israel, his internal clock was less disrupted and he was able to get the most out of his trip.

Hopefully this post has helped you see the light in that a little knowledge of physiology can help you feel and perform your best. And when the bad puns start up, it’s time to end. Thanks for reading!