The human body clock can
roughly shift about an hour each day as it synchronizes to the new
Major League Baseball (MLB) managers trying to find an edge should
pay close attention to their players' body clocks, according to a new
Northwestern University study of how jet lag affects MLB players
traveling across just a few time zones.
‘When people travel in a way that misaligns their internal 24-hour clock with the natural environment and its cycle of sunlight, they suffer negative consequences.’
The researchers found that when people, in this case Major League
Baseball players, travel in a way that misaligns their internal 24-hour
clock with the natural environment and its cycle of sunlight, they
suffer negative consequences.
"Jet lag does impair the performance of Major League Baseball
players," said Dr. Ravi Allada, a circadian rhythms expert who led the
study. "The negative effects of jet lag we found are subtle, but they
are detectable and significant. And they happen on both offense and
defense and for both home and away teams, often in surprising ways."
In a study of data spanning 20 years and including more than 40,000
games, the researchers identified these effects of jet lag on player and
- The offense of jet-lagged home teams is much more
affected than that of jet-lagged away teams. Surprisingly, in terms of
offensive performance, jet lag from eastward travel had significant
negative effects on home teams (after returning from a road trip) and
much less of an effect on away teams.
- Negative effects on offense are related to base
running. The negative effects on the home team's offense were related to
base running, such as stolen bases, number of doubles and triples, and
hitting into more double plays.
- Both home and away teams suffer on defense,
specifically by giving up more home runs. With defensive performance,
strong effects of eastward jet lag were found for both home and away
teams, primarily with jet-lagged pitchers allowing more home runs. "The
effects are sufficiently large to erase the home field advantage,"
Allada said. Besides home runs allowed, few other effects were seen on
pitching or defense.
- There is a difference between traveling east and
Most significant jet-lag effects were generally stronger
for eastward than westward travel. "This is a strong argument that the
effect is due to the circadian clock, not the travel itself," Allada
The study, "How Jet Lag Impairs Major League Baseball Performance," will be published in the journal Proceedings of the National Academy of Sciences (PNAS)
Allada and his team, Alex Song (first author) and Thomas Severini,
used an unprecedented amount of MLB data (from 1992 to 2011), which gave
the researchers the statistical power to identify the effects of jet
lag on offensive and defensive performance metrics. The researchers
considered if teams were traveling east or west; if the team was home or
away; and the team itself.
They also looked at the number of hours players would be jet-lagged,
based on the number of time zones traveled across, to determine which
games were "jet-lag games" and which were not. If players were shifted two or three hours from their
internal clocks, the researchers defined them as jet-lagged.
What does all this data analysis mean going forward? With MLB spring
training less than a month away, Allada has some advice based on his
"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," Allada said.
Allada provides an example from the 2016 National League
Championship Series illustrating the potential impact of jet lag on
player performance. In game two, Los Angeles Dodgers' ace Clayton Kershaw
shut out the Chicago Cubs, giving up only two hits, but game six was a
"For game six, the teams had returned to Chicago from LA, and this
time the Cubs scored five runs off of Kershaw, including two home runs,"
Allada said. "While it's speculation, our research would suggest that
jet lag was a contributing factor in Kershaw's performance."
Allada is the Edgar C. Stuntz Distinguished Professor in
Neuroscience and chair of the neurobiology department in the Weinberg
College of Arts and Sciences. He also is associate director of
Northwestern's Center for Sleep and Circadian Biology.