Jet lag can have a significant negative effect on how Major League Baseball teams perform, particularly — and surprisingly — after teams return to their home fields, according to a study published earlier this week in the journal Proceedings of the National Academy of Sciences (PNAS).
In fact, the effects of jet lag — defined in this study as traveling across at least two time zones — were enough to wipe out home-field advantages.
“Jet lag does impair the performance of Major League Baseball players, “said Ravi Allada, the study’s senior author and a neurobiologist at Northwestern University, in a released statement. “The negative effects of jet lag we found are subtle, but they are detectable and significant. And they happen on both offense and defense.”
While these findings are interesting to anyone who follows baseball, they also demonstrate how disruptions to the human body’s natural 24-hour, or circadian, biological rhythms can impact human performance.
Two decades of games
For the study, Allada and his colleagues analyzed data from 20 seasons (1992-2011) of Major League Baseball games. A total of 46,535 games were played during that period, of which 4,919 involved teams crossing at least two time zones.
For each of the games, the researchers examined offensive and defensive performance stats, including home runs, stolen bases, walks and sacrifice flies. They then analyzed how the stats differed for teams traveling east versus those traveling west, as well as how they differed when the jet-lagged team was playing at home (having just returned from a trip) or away.
As background information in the study points out, because the human body tends to run on an internal biological clock that is slightly longer than 24 hours, “it is generally thought to be easier to adjust to westward travel that delays sunrise/sunset, than eastward travel.”
Here are some of the key findings from the study:
- Most of the significant jet-lag effects are greater for eastward rather than westward travel. “This is a strong argument that the effect is due to the circadian clock, not the travel itself,” Allada said.
- Jet-lagged home teams are much more affected than jet-lagged away teams when it comes to offense. Those negative effects include fewer stolen bases, fewer doubles and triples, and more hitting into double plays. The only effects on away-team offensive performance appears to be fewer sacrifice hits and sacrifice flies, although the study couldn’t determine this for sure. The drop in on-field aggressiveness among jet-lagged home teams in the study was subtle, but seemed to make a difference. Teams in the study’s dataset won 53.9 percent of their games when they were playing at home, an advantage of 3.9 percent. But they were 3.5 percent less likely to win if they had just returned home jet-lagged from a west-to-east trip — a difference that essentially negated the home-team advantage.
- Eastward but not westward travel also affects pitching. Jet-lagged pitchers on both home and away teams tend to give up more home runs. “Not only are the effects of jet lag on pitching comparable to the effect of home-field advantage, those effects are largely explained by a single measure: home runs allowed,” write Allada and his colleagues.
Send starting pitcher ahead
The researchers can only speculate on why jet lag appears to have a greater effect on home teams. “One possibility is that the away team has a more structured daily schedule when away from home than does the home team when returning home,” they write.
As for jetlag’s effect on home runs, the researchers posed this hypothesis: “Pitching location and velocity appear to be important for determining the probability of giving up a home run relative to a swinging strike (swinging at and missing a pitch in the strike zone). Thus, we hypothesize that jet lag, particularly in the eastward direction, may adversely affect these aspects of pitching, which in turn impact home runs allowed.”
What can teams do to counter jet lag’s negative effects on performance? Perhaps change their travel protocol, said Allada.
“If I were a baseball manager and my team was traveling across time zones — either to home or away — I would send my first starting pitcher a day or two ahead, so he could adjust his clock to the local environment,” he explained.
FMI: The study can be accessed through the PNAS website.