The Plane Truth: Jet Lag in Sports
The National Football League, in an effort to enhance its popularity overseas, has scheduled an October 28th game between the New York Giants and Miami Dolphins to take place in London, the first regular-season game to take place outside of North America. So far, the response has been positive: the first 40,000 tickets to the game sold out in only 90 minutes. Recently, there have even been murmurs of transporting the Super Bowl across the pond as well, which would be kind of like playing the World Cup in the United States. With this heightened exposure, the NFL—and the paying British fans—want to make sure they are getting their pound’s worth. The one demon standing in the way is jet lag, an unavoidable consequence lurking in the background of all international sporting events. The demands of travel across multiple time zones have affected sports at least since the Brooklyn Dodgers moved to California in 1958, and jet lag casts an overwhelming shadow on the possibilities of international athletic league play.
Jet lag is not simply a consequence of too little leg room, stale air and Swanson-esque meals (mandatory Seinfeld bits here and here), and, of course, most professional athletes don’t have to deal with these problems anyway. Jet lag is mostly due to alterations to an individual’s natural circadian rhythm, which is the roughly 24-hour cycle (circadian is from the Latin, meaning “about a day”) of variations in all sorts of, literally, everyday occurrences. While the sleep-wake cycle is what we most often associate with circadian patterns, we also experience daily peaks and valleys in metabolism, body temperature, hormone release, and, evidently, interest in cable news topics.
The sun has been here longer than us (Gen 1:3-5), so creatures of all sorts, from microscopic organisms to plants to humans, have developed circadian rhythms to take advantage of solar energy and the regular light-dark cycle. These biological clocks act to synchronize the body with predictable environmental events, although the specific cyclic physiological and biochemical processes that promote healthy functioning vary greatly between species. For instance, hatching of the fruit fly drasophila pseudobscura occurs only in the morning so they can stretch and dry their wings when humidity is high. Many small rodent mammals are most active at night, when susceptibility to predators is lower. For our cave-mancestors, daylight provided time to scavenge for food and meet cavebabes. Thus, nightfall was best for rest and rejuvenation, and sleeping in one’s cave had the added benefit of avoiding getting eaten by saber-toothed tigers.
Other rhythms complement our natural sleep patterns. The adrenal glands release the greatest amounts of the stress hormone cortisol just prior to or immediately after awakening. This action isn’t simply a response to the war you wage with your alarm clock—it actually helps you get moving in the morning, which is why we often wake up, regrettably, at about the same time on the weekends. Metabolism slows down overnight, and melatonin and growth hormone are released. Body temperature, on the other hand, peaks in the mid-afternoon. This orchestra of cyclic variation helps us to function optimally on a daily basis.
The circadian rhythm is an endogenous mechanism, persisting in its approximate 24-hour period even in the absence of external cues, such as in a constant dim light. However, the cycle can be subject to environmental influences known as a “zeitgeber” (my sources say the word is “from the German,” but it clearly is German, meaning “time giver”). Light serves as the most potent zeitgeber in humans and most organisms, as mediated by the suprachiasmatic nucleus (not a Mary Poppins song; SCN) in the hypothalamus. The SCN acts as the locus of our circadian rhythm, and it receives direct projections from the light-sensitive ganglion cells in the retina.
While today we are less a slave to the light-dark cycle of the sun, the daily pattern remains, staying relatively constant in the absence of changes to our environment. Even for our prehistoric brethren, though, circadian rhythms obviously weren’t set in stone, due to seasonal changes in daylight length. However, our internal clocks are not meant to deal with rapid trans-timezonal transportation. Jet lag is a direct consequence of immediate disruptions to our circadian pattern, with symptoms that include sleep disturbances, digestive problems, malaise and a variety of psychological impairments. The general rule is that these symptoms last about a day for each time zone crossed.
And now, finally, back to sports. When athletes travel across time zones, the main effects on performance are two-fold: (1) The direct effects of jet lag, as stated above; and (2) The effects of participating in events at non-optimal times according to their biological clocks.
The direct consequences of jet lag on athletic performance are primarily psychological. Impaired perception and attention follow from the desynchronization of the circadian rhythm, which should be particularly devastating for hand-eye coordination. These impairments are present even following slight changes to our rhythm, as demonstrated by increases in traffic accidents immediately following the “spring ahead” portion of daylight savings time. Other harmful factors include worsened mood and motivational deficiencies, which may lead to poorer performance on the field of play when the going gets tough, or perhaps an exaggerated response to bad calls. The severity and duration of these problems may depend on the direction of travel: numerous studies have shown that jet lag is more prominent for eastbound travelers than for westbound travelers, probably because it’s easier to stay up late than go to sleep early.
So, you say, why not just avoid jet lag by remaining on the same schedule, regardless of local time? Well, for one, the zeitgebers won’t have any of that. Outside constraints, including sunlight, noisy hotel guests and social customs, beg you to join the circadian pattern of the local area. Also, staying on the same pattern won’t necessarily help, as you’d likely be competing outside of your peak time range. On a variety of measures, peak strength and aerobic performance occur in the late afternoon and early evening hours. Competing at these optimal times can result in as much as a 10% increase in performance. Individuals demonstrate greatest muscle strength, regardless of muscle group, between 2 and 7pm. Performance on a swim test or a cycling time trial is also best in the early evening, around 6 or 7 pm. Notably, these peaks occur even with adequate warm-up time to ensure that flexibility or body temperature (which are typically lower in the mornings) were not the main reason for the detriment. Also, these times of peak performance exist even when training has routinely taken place in the morning.
Fortunately for fans and TV producers, most sporting events are scheduled to start in the early evening, so all is well and good for competitors. But when the New York Mets travel to play a night game at the Los Angeles Dodgers, the game starts past their time of peak performance, assuming the Mets’ players are on a New York schedule (not a Billy Joel song). In NFL games, west coast teams facing east coast squads on Monday night, with games starting at 9 pm EST, performed significantly better than predicted by Las Vegas oddsmakers, regardless of which coast the game was played, as the west coast team was playing closer to their circadian peak in each case. In fact, west coast teams beat the point spread in 67.9% of these games from 1970-1994, which would be outstanding knowledge if, you know, gambling was legal. Of course, one would expect the reverse, though not as drastic, effect for games played at 1pm Eastern time (no data on this aspect is available).
Performing at a time outside of your circadian athletic peak isn’t always a problem, though. In events in which arousal can be a detriment and muscle steadiness is necessary, such as archery, competing during your biological morning may be beneficial. The accuracy of tennis and badminton serves is actually better during the early afternoon (2 pm). Here, flying across an ocean may help if the event is scheduled for evening local time—in theory, that is, assuming you’re not stressed, or fatigued, or swigging Pepto.
With professional sports teams, its unclear how much of a factor these jet lag effects may play, particularly in sports such as baseball and basketball where travel is relatively constant and the circadian rhythm may not be as established. However, professional American football players do spend a majority of their time in a single time zone, so the long travel to London may be detrimental to their play, even though the game is schedule for 1 pm Eastern time (6 pm local). The NFL schedule makers have been kind enough to grant both the Giants and the Dolphins a week off following their trans-Atlantic venture. A better idea, given the greater effects of jet lag on eastbound travel, would have been to schedule the teams’ bye week for the week immediately prior to their London game. Nonetheless, I recommend the teams to travel to Britain as soon as possible following the preceding game in order to minimize jet lag effects and play at their maximal abilities. Just think of it as a way to enjoy the sites, perhaps catch a match of what they call football, or maybe have a bite of what they call food.
Reilly T, Marshall S. 1991. Circadian rhythms in power output on a swim bench. J Swim Res. 7(2), 11-13.Smith RS, Guilleminault C, Efron B. 1997. Circadian rhythms and enhanced athletic performance in the National Football League. Sleep. 20(5), 362-65.
You probably didn’t learn about the scientific method in your junior high gym class, and not too many post-game interviews touch on quantum theory. But don’t be fooled: the athletic and scientific worlds are not such strange bedfellows. Boxing, for instance, is often called “the sweet science.” And no less an expert than Ted Williams, perhaps baseball’s greatest batter, described his craft in his book, The Science of Hitting. We turn our focus to this intriguing relationship here in Sportsology, where we endeavor to examine the world of sports with a scientific eye. Sportsology will explore athletic topics you never knew you cared about, from the physics of the curveball to Olympic abstinence. We hope to arm you with knowledge to, at the very least, make you the most annoying person at the sports bar.
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