Jet lag can put anyone off their game, even Major League Baseball (MLB) players. Long-distance travel can affect specific—and at times, crucial—baseball skills such as pitching and base running, a new study finds. In fact, jetlag's effects can even cancel out the home field advantage for some teams returning from away games.
Jet lag is known for its fatigue-inducing effects, most of which stem from a mismatch between a person’s internal clock and the time zone he or she is in, something called “circadian misalignment.” This misalignment is especially strong when a person’s day is shorter than it should be—which happens whenever people travel east—previous research has shown. Just how that affects sports teams has long been debated. A 2009 study of MLB, for example, found that jet lag did decrease a team’s likelihood of winning, if only slightly.
But no prior study has ever been able to pinpoint exact areas of game play where the effects of jet lag hit hardest—data that could help coaches and trainers better prepare players for games following travel. To figure out how that might happen, “adopted” Chicago Cubs fan and study author Ravi Allada, a neurobiologist at Northwestern University in Evanston, Illinois, looked at 20 years’ worth of MLB data from 1992 to 2011. He and his team narrowed their data set from 46,535 games to the 4919 games in which players traveled at least two time zones. Then, they broke down offensive and defensive stats from each of those games, including home runs allowed, stolen bases, and sacrifice flies. Finally, they compared how the numbers changed for teams that had traveled east versus those that had traveled west.
The effects were almost always worse for teams going east, the researchers report today in the Proceedings of the National Academy of Sciences. “One of the more surprising things we found was that in some cases we would see effects on home teams and not away teams,” Allada says. “We don’t typically think of home teams as suffering jet lag, but that’s what we observed.”
Home teams played less aggressive offense after traveling, especially if they had just traveled east. In such games, players were less likely to attempt doubles, triples, and stolen bases, all of which require bolder base running. Eastward travel could even cancel out a team’s home field advantage: For example, home teams won 53.9% of the time in the entire 46,535-game data set. But if a team like the Cubs returned to Wrigley Field after playing a series in Los Angeles, California, they were 3.5% less likely to win—effectively removing their advantage.
“Teams expect there to be a problem when they travel on the road, but I don't think anybody really thinks about the problems that could occur when they return home,” says Aaron Lee, a sports medicine physician at MacNeal Hospital in Chicago, Illinois, who conducted his own review of jet lag in athletes in 2012. One of the more striking finds in the new study, he says, was that jet lag significantly impacted both home and away team pitchers’ ability to prevent home runs. That makes sense, he adds, because jet lag tends to affect actions that require complex cognition and fine motor skills. “The act of pitching is very fragile. It doesn’t take much to throw it off.”
Ben Edwards, a chronobiologist who studies circadian rhythms at Liverpool John Moores University in the United Kingdom, says the data “adds positively” to the current literature. But he still has some reservations. For example, many factors can’t be controlled for in a retrospective study; travel schedules, game times, and how rested individual players are can all make a difference, he wrote in an email to Science.
"Retrospective studies are a challenge from the outset because all the factors that are controlled for in a lab setting that we’re so fastidious about are lacking,” says Colin Robertson, a chronobiologist in the sport sciences department at the University of Bolton in the United Kingdom, who was not involved in the work. “This [study] was really ambitious.”
Allada’s next step is to use the new findings to examine how jet lag might affect a single team or even individual players. Robertson says he hopes to see that happen. “If you could take one of those teams and track them for a season … and then look at what time of day they train or what time of day they produce their best performance [following travel],” he says, “that would be phenomenal, and that’s never been done before across any sport.”