Years worth of training, competition, and trust come to fruition this weekend as my teammate, training partner, and friend competes for the title “Fittest on Earth.” I’ve talked about the Crossfit Games and the journey that it takes to get there many times before. Last year, I had the opportunity to compete on a team with Emily in the Games. This year, I cheer on Emily Bridgers from Atlanta, regretting not being there in person to support (because science calls). Emily is going to impress everyone this weekend–fans, judges, coaches, other athletes, and the ESPN networks.
While athletes are prepping for the Games, I bet many of them overlook one important variable: jet lag. The Games are in California but represent teams from around the world. Jet lag can have residual effects on rhythms of physiology and behavior beyond just a day. Depending on the direction and extent of travel, it can sometimes take a week to adjust, mentally and physically. With that, I provide an excerpt from my book that is due on bookshelves within the next year–Meathead. This particular chapter discusses the impact of jet lag on game day performance.
“There actually is a handful of information on jetlag, sleep deprivation, and their consequences on athletic performance. Most of the laboratory-based studies have focused on shifts in rhythms of melatonin and CBT, which are easy to measure with little invasiveness. As I discussed earlier in the chapter, the relationship between CBT, sleepiness, and mental and physical performance is intimate; drops in CBT increase sleepiness which lead to declines in mental and physical performances. With a new light schedule, especially one that is more than a few hours ahead or behind, the release of melatonin—the “hormone of darkness” that is sensitive to light— is suppressed and the normal afternoon and early morning dips in CBT occur earlier or later. Obviously, both of these physiological shifts wreak havoc on sleep and performance by keeping people up at night, waking people up too early, and causing a lack of focus and energy throughout the day. In fact, one study has compiled a breakdown of motor and mental skills that suffer from insufficient sleep driven by game day travel; for low-aerobic sports that require high levels of alertness and fine motor skills like sailing and archery, there’s more room for error. For team sports that require high levels of concentration, there’s poorer decision-making. For individual sports with a mixture of aerobic and anaerobic movements like swimming, mixed martial arts, and weightlifting, there’s a loss of power and quicker time to fatigue. Although these symptoms and changes in our body’s physiology from game day travel across time zones eventually disappear, the problem is that it takes at least a few days for the body to adapt. For professional baseball and basketball players, this is an unresolvable problem because many teams are already on their way to a new time zone to play another team. As an example, the 2012 NBA season, which was truncated by contract agreements, had more game-day travel than in year’s past to make up for lost inter-conference playing time. The season was also plagued by poor refereeing, increased amounts of injuries, and complaints of constant exhaustion. Although no empirical studies were undertaken, sports pundits and researchers like me believe that jet lag and constant weekday and weekend game travel were the culprits28.
In the field of sleep research, we often talk about “sleep debt” which refers to any negative deviation from your body’s desired amount of nightly sleep. So if your body requires 8 hours and 20 minutes of sleep a night (the human average), but you only get 7 hours, you will need to make up that 1 hour and 20 minutes at some point. If we short-change ourselves 1-2 hours of sleep for a few days once a year, this isn’t a big deal. We may be sleepy for a few days, but we will rebound quickly. But if we are depriving ourselves of 1-2 hours of sleep a few times a week for months or years, we aren’t getting quality sleep. This is largely because our body full of clocks keeps getting exposed to different light-dark cycles, which is a serious problem. Under these circumstances of chronic sleep deprivation, our sleep debt creeps up on us whenever we aren’t socially stimulated such as when we are driving, watching a movie, or standing around in the outfield. Even if we aren’t sleepy per se, our minds are slower due to individual neurons going offline at random intervals to “rest,” and our physiological rhythms of growth hormone which acts to repair damaged and maintain healthy tissue can be suppressed. This is one of many reasons why game travel in collegiate and professional sports communities should be re-evaluated or more carefully planned with the help of researchers in sleep and circadian rhythms.
Does the length and direction in which we travel also make a difference? That is, does performance suffer worse upon travel to the Pacific versus Mountain time zone from the East Coast, or do West Coast teams playing a night game at home have a physiological advantage over their East Coast opponents or vice versa? If you look at the regional distribution of professional NFL, NBA, and MLB teams across the US, nearly half the teams lie in the Eastern US time zone (Atlantic coast) while a majority of the others are in the Central or Pacific US time zones (Midwest or Pacific coast). Within a professional organization, there are two conferences that are not solely determined by region of the country; both the MLB and NFL are divided into American and National Leagues which each have teams on the West Coast(Oakland A’s for American and San Diego Padres for National) and East Coast (Boston Red Sox for American and New York Mets for National). This is particularly bothersome for Major League baseball players who play 2-4 games per week, sometimes in different time zones, versus a professional football player with one game on a Monday, Thursday, or Sunday. Luckily for us, researchers have investigated if the type of game (away versus home) and direction of travel (east versus west) impacts athletic and mental performance through careful examination of win-loss records, changes in individual statistics, and even a few questionnaires on sleep habits.
Even with mice and hamsters, the direction of travel makes a difference; mice have an easier time adjusting to delays in their light-dark cycle, whereas hamsters have an easier time adjusting to advances. This time zone preference actually isn’t random either, but rather explained by how closely biological clocks “tick” towards 24 hours. Because the biological clock of a mouse “ticks” slightly less than 24 hours, a delay in an environmental schedule would make their clocks “tick” at 24 hours. Meanwhile, because the biological clock of a hamster “ticks” slightly more than 24 hours, an advance in an environmental schedule would make their clocks “tick” at 24 hours. Human biological clocks are similar to those of a hamster in that they “tick” slightly longer than 24 hours. This is why most humans have an easier time with Western versus Eastern travel. Athletes are no different. One of the first studies to investigate athletic performance following East versus West Coast travel was determined from archived data of the 1996 collegiate (NCAA) football season; the University of Florida Gators were national champions that year. Overall, teams that traveled more than one time zone eastward performed consistently worse than teams traveling more than one hour westward: they scored fewer points, allowed more points, and had greater point spreads even when controlling for progress of the game: 1st quarter versus 4th quarter29.
In terms of whether travel to the Pacific coast versus Midwest for a New York Yankee matters, it does. In 2008, I learned about such a concern at our annual sleep conference held in Baltimore, Maryland through Dr. W. Christopher Winter at the University of Virginia who happened to have a research poster next to me. Dr. Winter and colleagues entered the scores of over 24,121 MLB games into a database that controlled for number of time zones travelled. Independent of direction, 60% of games were lost if the baseball player traveled three zones and 52% were lost for travel through two time zones. An 8% difference may not seem significant, but in the world of professional sports that can be the difference between finishing last in the league (and subsequently getting first pick in the next year’s draft) and vying for a pennant. These results–that athletic and mental performance suffer more as the number of time zones travelled increases–make biological sense because that extra hour of light (or dark) for one more time zone would mean that your body would need an extra day and sometimes more to adjust. However, there are many strategies for adapting quicker to a new time zone of which I’ll discuss next.
As for whether certain coastal teams have an advantage during night games–the games with the highest viewer ratings–this also matters. The sleep community of Stanford University conducted a carefully controlled examination of win-loss records across forty years of play in the NFL to determine if East Coast teams had a biological advantage over West Coast teams during a night game played on the East Coast or if West Coast teams had a biological advantage over East Coast teams during a night game played on the West Coast. Unlike previous studies, these researchers also factored in the Vegas point-spread which is carefully calculated: it is based on win-loss record, injury reports, historical matchups between the teams, weather, and whether it is an away versus home game plus many other variable. Therefore, a “win” in this Standford study was defined as winning the actual game and beating the Vegas point-spread. Unfortunately, East Coast teams are always at a disadvantaged when playing a night game with West Coast teams winning 70 out of the 106 night games played regardless of whether it was an away or home game. So even if an athlete is at a biological disadvantage to performing at their best due to game day location, can modern science and medicine help?