The importance of jet lag and rest in baseball

One of the more interesting pieces of baseball news this week was a study on jet lag and how it affects performance in MLB.

The study was performed by Alex Song, Thomas Severini and Ravi Allada and published by the Proceedings of the National Academy of Sciences, analyzing 20 years (1992-2011) and 46,535 games of data. Specifically, they were interested in teams that traveled at least two time zones, and the immediate effects on performance.

A summary:

Accounting for potential differences in home and away performance, travel direction, and team confounding variables, we observed that jet-lag effects were largely evident after eastward travel with very limited effects after westward travel, consistent with the >24-h period length of the human circadian clock. Surprisingly, we found that jet lag impaired major parameters of home-team offensive performance, for example, slugging percentage, but did not similarly affect away-team offensive performance. On the other hand, jet lag impacted both home and away defensive performance. Remarkably, the vast majority of these effects for both home and away teams could be explained by a single measure, home runs allowed. Rather than uniform effects, these results reveal surprisingly specific effects of circadian misalignment on athletic performance under natural conditions.

With the west coast generally more spread out than the east coast, and with a higher density of teams eastward, teams out west travel much more than those in the central or east.

In 2016, no team traveled more miles than the Mariners at 47,704, almost double that of the Cubs, who traveled the least at 24,271 miles, per MLB.com. The Dodgers were among the most-traveled teams last year, fifth at 40,294 miles. The MLB average was 32,714 miles.

This jet lag study struck a nerve with me because I remember tracking Dodgers travel in 2015 because they had such a long losing streak after traveling. That year the club was 1-11 in the first game after traveling at least two time zones, east or west. Their lone win was the last such game of the season.

I took a look at the Dodgers schedules from 2014-2016 to find these situations when they traveled at least two time zones. Some facts from the last three years:

• Dodgers were 16-25 (.390) overall.
• They were 9-7 (.563) at home, which is good but also well under the club’s Dodger Stadium record the last three seasons (153-90, .630).
• They were 7-18 (.280) on the road in such games.
• Dodgers were 6-15 (.286) when traveling east at least two time zones, including 4-6 (.400) when traveling three time zones east. It should be noted that all 3-zone trips east included one off day for travel.
• When traveling east two time zones but with no off day, the Dodgers were 1-5 (.167).
• When traveling west two or three time zones but with no off day, the Dodgers were 8-9 (.471). They were 2-1 (.667) traveling west with an off day built in.

Looking ahead to the 2017 schedule, the Dodgers have 13 trips scheduled of at least two time zones. Six of those trips head east, including five 3-zone trips, all with an off day built in. There are seven trips west — four 3-zone trips and three 2-zone trips — and the only such trip with an off day built in is a 3-zone trip from New York (Aug. 8) to Phoenix (Aug. 10).

Given that the main noticeable effect of jet lag was an increase in home runs allowed, the study suggests that teams get more aggressive in sending starting pitchers to the next city as many as a few days ahead of time to allow more time to recover, rather than the current practice of sending a pitcher maybe hours or a half-day ahead of time.

I’m not sure if teams will be that aggressive in sending their starting pitchers ahead, but the issue of travel and jet lag is certainly taken seriously within baseball. The Dodgers have had sleep consultants visit the team in recent years, most notably suggesting the use of a special light in 2014 to help account for the trip to Australia.

The issue of player fatigue and rest was addressed in the new collective bargaining agreement as well, though most of those changes don’t take effect until 2018. Starting next year, the regular season will last 187 days instead of 183, allowing for four more days of rest built into the schedule, and there are more restrictions on start times in an attempt to maximize time for travel and rest between trips.