The growth of the SC2 scene in recent months has been staggering. From the GSL in Korea, to MLG in the US, to Dreamhack in Europe, the scene has truly become international. As a fan, this is fantastic. But for a pro, it can mean a hell of a lot of traveling. Players like HuK and MC now seem to spend as much time airborne as they spend crushing nerd skulls. This is obviously not ideal, as it means players may not be in top condition, and may even risk burn-out.
For my 750th post, I present a basic guide to understanding and dealing with jet lag. While this is motivated by the pro-tournament scene, I hope it will be useful to pro and everyday travelers alike.
First off, we need to understand why jet lag happens, and that means talking about the circadian clock.
Imagine you were placed in a darkened room for a week, with a comfy bed and no clue as to what time it was outside. You could sleep whenever you wanted, and meals would be provided whenever you requested.
How do think you would sleep under these conditions? Try to guess before you read on.
So, you might have guessed that you would lose any regular schedule and start napping on and off around the clock. Well, it turns out that's not what happens. People have actually done these experiments, and found that even in the absence of external time cues, people continue to follow an approximately 24-h sleep/wake cycle. This graph is an example of somebody who knew what time of day it was for 21 days, and then had all external time cues removed for a couple of months.
Along the horizontal axis is time of day, and along the vertical axis is the number of days into the experiment. The dark bars indicate times when the person was asleep. What you can see is that they maintained a regular schedule for the first 21 days, always going to bed around 2am, and waking around 10am.
After time cues were removed on day 22, you can see that they started to go to bed about an hour later each day, meaning they were living on an approximately 25-hour day. This is not done consciously; it is all down to the fact that our bodies are regulated by an internal biological clock. This clock is commonly referred to as the circadian clock, because its natural cycle length is about 24 hours (circa = about, dia = day).
Just about every form of life has a circadian clock, as a result of having evolved in the presence of a daily light/dark cycle. Jet lag is the natural result of rapidly moving to a different time zone, a situation that never arose during the course of evolution.
As you just saw, when all time cues are taken away, the circadian clock keeps the body running on a schedule close to, but not exactly, 24 hours. In fact, for humans, the average circadian period is around 24.2 hours. Different people have slightly different periods, but they are all within an hour of this value.
Now, as you might imagine, if the circadian clock is going to remain synchronized to the 24-hour Earth day, it needs to be readjusted slightly each day to make up for the difference between its own period and 24 hours. For people with circadian periods greater than 24 hours, this will mean a slight advance of the clock (i.e., setting it forward), while for people with circadian periods less than 24 hours, it will mean a slight delay of the clock (i.e., setting it back).
So what is it that resets the clock to the correct time each day? It turns out the answer is light. Without light, the clock will continue running at its own period, oblivious to the 24-hour day, and in fact this is a condition suffered by many blind people.
Exposure to light can either advance or delay the clock, depending on when in the circadian cycle it occurs. The following chart shows how this works.
So light you receive in the morning tends to advance your clock (i.e., set it forward), while light you receive late in the evening tends to delay your clock (i.e., set it back). How much light do you need to have a significant effect on the clock? Not much at all. Room light, despite being around 1000 times dimmer than sunlight is still about half as effective.
This is helpful practical knowledge, because it means if you stay up late gaming one night, it will delay your circadian clock. This means you will want to go to bed later on the following night, which can quickly become a habit. To break this cycle, it's best to minimize light exposure at night, and maximize it in the morning (e.g., open your curtains, take a morning walk). It's also worth noting that the circadian clock is most affected by blue light; this free program, which changes the color balance of your monitor, is one way of reducing your blue light exposure late at night.
When you move suddenly to another time zone, your circadian clock is still set to the time zone you just left. This is why you tend to feel sleepy or hungry at unusual times, and just generally messed up. So long as you don't do anything crazy, the circadian clock shifts by about 1 time zone per day. Unfortunately, this isn't quick enough for pros jetting straight between tournaments.
Adapting to a new time zone can be sped up by maximizing or minimizing your light exposure at appropriate times. Here are some tips for maximizing your light exposure:
1) Turn on more lights.
2) Get exposure to sunlight, if possible.
Here are some good ways to minimize light exposure:
1) Stay indoors if the sun is out.
2) Wear sunglasses.
3) Turn off lights.
4) Take a nap! The circadian clock only receives light through the retina, so anytime you are asleep, there is zero light input.
I'll explain when you want to maximize or minimize your light exposure using some examples. But first, here's a helpful trick
You can use your wristwatch to record what time your circadian clock thinks it is.
Here's how to do it:
1) Before your trip, make sure your watch is set to your local time.
2) For every day in which you attempt to shift your circadian clock to the new time zone through managing your light exposure, set your watch time 1 to 2 hours closer to the target time zone. Shift 1 hour if you feel you didn't do a particularly good job of managing your light exposure. Shift 2 hours if you feel you did a good job of managing your light exposure. If you feel you did absolutely everything wrong (received a lot of light when you shouldn’t have, and were in dim light when you should have been in bright light) don’t change your watch time for that day.
Now, life is easy. Just follow these simple rules:
1) If your clock reads anything between 9am and 2pm, light will ADVANCE you (i.e., set your circadian clock forward).
2) If your clock reads anything between 9pm and 2am, light will DELAY you (i.e., set your circadian clock backwards).
3) If your clock reads anything between 2am and 9am, you should try to sleep, or minimize light exposure if you are awake.
Let's start with an example of flying west: from Los Angeles to Seoul.
Seoul is 17 hours ahead, or 7 hours behind, if you prefer to think of it that way. So at 8pm in Seoul on the day you arrive, your circadian clock thinks it's 3am (the time in Los Angeles). This is bad news if you have a game scheduled for this time. Your concentration will be impaired, your reactions will be sluggish, and will likely feel cold through, as your body lowers its core temperature in expectation of sleep.
Without any special interventions, the circadian clock will typically take about 7 days to shift across the 7 time zones between Los Angeles and Seoul. This shifting occurs due to the new light/dark cycle.
Because the sun now rises and sets 7 hours later, there is more light exposure at times when light causes delay. This results in the clock gradually resetting later and later until it has reached Seoul time.
Artificial light can of course mess with this, so we need to be take care in understanding whether switching the light on when it's dark outside will help the adaptation.
In this example, we want to delay the clock as much as possible. This means maximizing light exposure at times when your watch reads 9pm to 2am, and minimizing it otherwise.
Note that you can (and should) begin shifting your clock before you actually take your flight. In this example, if you can shift your circadian clock some of the way before you leave, you will only need to shift a small way once you arrive in Seoul.
So, suppose you fly out of LA on June 10. You can start your shift on June 8 by minimizing light exposure between 9am and 2pm, and staying up a little later to maximize light exposure between 9pm and 2am. You can now set your watch back 2 hours for June 9 (i.e., when it's 9pm in Los Angeles time, the watch will read 7pm). You should follow the same procedure on June 9, minimizing light exposure when your watch reads between 9am and 2pm, and staying up a little later to maximize light exposure when your watch reads between 9pm and 2am. You can now set your watch back another 2 hours for June 10 (i.e., when it's 9pm in Los Angeles, your watch will now read 5pm). The flight will arrive in Seoul on June 11. Let's suppose on the trip to Seoul it was difficult to manage light exposure, so we only shift the clock back 1 hour for June 11. This means your clock is now 5 hours behind Los Angeles time, which is only 2 hours off Seoul time. In just a couple more days you should be fully adapted to Seoul time.
The chart below shows the shifting watch time for this trip, along with the light exposure from 9pm to 2am each day.
While flying west is all about delaying the clock as fast as possible, flying east is all about advancing it (so long as you are not crossing more than 8 time zones – for that case, see the points in the last section). As an example, let's consider a flight from New York to Stockholm.
Stockholm is 6 hours ahead of New York, so we need to advance the clock (i.e., set it forward) as quickly as possible. Natural light exposure will help matters, but we can speed the adaptation by following the watch rules as above. Whenever the clock reads 9am to 2pm, we should maximize light exposure, and whenever it reads 9pm to 2am, we should minimize light exposure.
So, suppose you fly out of New York on October 10. You can start your shift on October 8 by getting some extra morning light, and minimizing light exposure between 9pm and 2am by switching lights off, and getting an early night. You can now set your watch forward 2 hours for October 9 (i.e., when it's 9am in New York time, the watch will read 11am). You should follow the same procedure on October 9, maximizing light exposure when your watch reads between 9am and 2pm, and turning off the lights and getting to bed a little earlier to minimize light exposure when your watch reads between 9pm and 2am. You can now set your watch forward another 2 hours for October 10 (i.e., when it's 9am in New York, your watch will now read 1pm). The flight will arrive in Stockholm on the morning of October 11. Let's suppose on the trip to Stockholm it was difficult to manage light exposure, so we only shift the clock forward 1 hour for October 11. This means your clock is now 5 hours ahead of New York time, which is only 1 hour off Stockholm time. In just another day you should be fully adapted to Stockholm time.
For pros, travel itineraries can be a lot more complicated than a single trip east or west. Often a series of tournaments will be played in different locations. Or in the case of ongoing series like the GSL, a player may take an excursion to another tournament in the midst of the season before returning for the next round.
In these cases, the same rules can be applied to speed adaptation to a new time zone. But here are some extra tips to help you cope with jet lag:
1) When traveling across a very large number of time zones (more than about 8), the circadian clock always finds it easier to delay than advance. So, for instance, if you are flying 10 time zones east, it is actually easier to delay your circadian clock 14 hours rather than advancing it 10 hours.
2) Sleep is important! If you are feeling out of it and it's not a time scheduled for light exposure, take a nap!
3) Sometimes it will be impossible to avoid playing at an adverse circadian phase. By that I mean, when your watch is telling you that it's the middle of the night. Well, there's still something you can do - have some coffee! Remember that caffeine ingested orally takes about 1 hour to reach its peak level, and has a half life of about 7 hours, so plan ahead!
4) Stay off melatonin unless you really know what you're doing. Melatonin can help you get to sleep, but it also resets the circadian clock. If you take it at the wrong time, it may actually make your jet lag worse!
5) Food intake also has some effect on the circadian clock. It may therefore be beneficial to switch your meal times to the target local time as soon as possible to improve adaptation.
Finally, if you're a pro player with a complicated travel plan, feel free to PM me and I may be able to give you some additional pointers for your schedule.