What the NBA bubble taught scientists about jet lag

To save sports and avoid a coronavirus catastrophe, the NBA paused play in mid-March as the pandemic worsened. But in July 2020, the league rebooted – this time not in stadiums around the country, but in a meticulously designed "bubble" at Disney World.

The NBA bubble included a laundry list of precautions: extensive quarantines, testing and tracing protocols, smart rings and proximity trackers, social distancing and mask-wearing, and limited outside contact. The effort was worth it. The NBA finished its season without a single player, coach, or staff member testing positive for Covid-19.

This controlled environment limited Covid-19's spread. It also gave scientists the opportunity to pinpoint the factors shaping a team's wins or losses.

In a recent study, researchers unwound the biological mechanisms behind a home-court advantage. Jet lag, body clock disturbances, and bad sleep were all revealed to hurt performance and accuracy. The findings were published December 11 in the journal Scientific Reports.

These unintended side effects of travel may be more influential than the roar of a home team's fans or referees' bias.

Based on these insights, researchers say it is possible to counteract jet lag's negative effects by getting where you're going as quickly as possible. These findings, in turn, can go beyond the court: Strategies gleaned from the research could help non-athletes taking an exam or workers giving a make-or-break presentation after travel.

Why study sleep — Andrew McHill is an occupational health scientist at Oregon Health & Science University who specializes in sleep disturbance and circadian rhythms. McHill tells Inverse that, when the NBA bubble emerged, he was eager to study how travel impacted basketball players' performance.

McHill is especially interested in the body clock — and how screwing with it can alter game time play.

Every person, athlete or not, has an internal body clock or circadian rhythm set to about 24-hour cycles synchronized to dawn and dusk. Our body clocks influence sleep patterns, mood, food cravings, immune function, and body temperature. When they're knocked out of whack — due to sleep deprivation, all-nighters, or travel schedules — this mismatch sets off a range of negative side effects.

"When we travel quickly to new time zones, and a subsequent new light/dark cycle, our internal body clock can’t adapt quickly enough," McHill explains.

"You get a mismatch between the central circadian clock in the brain’s hypothalamus with external behaviors. Thus, your central clock is continuing to promote certain behaviors such as rest, inactivity, sleep at the time it typically would."

In the NBA, this becomes a problem when a basketball player on an East coast team is playing an evening game out West. When they should be sleeping, they're in the third quarter.

What was discovered — To examine how these body clock disturbances affect athletes, McHill and his team compared the performance of 22 NBA teams during their regular, traveling season before the pandemic against their performance in the bubble.

The scientists examined 649 games played at home before the Covid-19 shutdown, 715 games played when traveling “away” before the shutdown (including games in different time zones), and 176 games played after all teams lived and played in the bubble for their final eight regular-season games.

Performance-wise, researchers evaluated winning percentage, shooting accuracy, rebounding, and turnovers.

"Misaligning your internal body clock by crossing time zones impairs precision and accuracy."

When teams traveled within their own time zone and across others, they performed significantly differently. Teams performed optimally and had improved shooting accuracy and rebounding when they didn't travel at all.

Shooting accuracy was affected by travel across time zones, whereas rebounding was more impacted by travel in general.

"Misaligning your internal body clock by crossing time zones impairs precision and accuracy," McHill tells Inverse. "Travel in general, including staying within the same time zone, impairs effort-related statistics which could be driven by impaired sleep and the rigors of travel."

Players were significantly less likely to win when traveling across time zones, especially traveling westward. These teams experiencing jet lag had worse shooting accuracy and decreased effort overall.

Why this matters — These jet lag findings jibe with ESPN's 2019 reporting on the "NBA grind" and the chronic lack of sleep due to each season's breakneck pace. It's the "dirty little secret that everybody knows about," journalist Baxter Holmes reports.

NBA teams typically play 82 games in under six months and fly up to 50,000 miles per season — roughly 20,000 more miles each season than NFL teams and far enough to circle the globe twice, per ESPN. In turn, players are chronically deprived of sleep, a scarcity that's hurting their performance on the court as well as their mental and physical health off of it.

This latest study helps quantify travel's toll on athletic performance — while also offering insights for anyone who struggles to balance work with the sleep they need.

"This study highlights the fact that we should prioritize sleep when possible and attempt to do activities when our internal body clock is optimally promoting those activities to be done," McHill says. Specific examples include sleeping during the night or eating and being active during the day.

Based on these discoveries, McHill argues travel schedules and game strategies could be redesigned depending on the type of travel happening before a sporting event. Future experiments with sports teams will reveal exact adjustments to mitigate the negative jet lag effects.

Beyond athletics, everyday people should also consider how different types of travel may impact their work performance or ability to enjoy a vacation.

"To shift or reset the body clock to support optimal performance, an individual could simulate the new light/dark cycle of the new time zone ahead of time and shift the clock to synchronize with that time," McHill says. In sports, this could be really difficult, but little changes could go a long way, he adds.

"If possible, arriving to your new time zone as early as possible without sacrificing sleep could be beneficial to synchronize to that new location and improve performance," McHill says.

Abstract: On March 11th, 2020, the National Basketball Association (NBA) paused its season after ~ 64 games due to the Coronavirus 2019 (COVID‐19) outbreak, only to resume ~ 5 months later with the top 22 teams isolated together (known as the “bubble”) in Orlando, Florida to play eight games each as an end to the regular season. This restart, with no new travel by teams, provided a natural experiment whereby the impact of travel and home‐court advantage could be systematically examined. We show here that in the pre‐COVID‐19 regular season, traveling across time zones reduces winning percentage, team shooting accuracy, and turnover percentage, whereas traveling in general reduces offensive rebounding and increases the number of points the opposing (home) team scores. Moreover, we demonstrate that competition in a scenario where no teams travel (restart bubble) reduces the typical effects of travel and home‐court advantage on winning percentage, shooting accuracy, and rebounding. Thus, home‐court advantage in professional basketball appears to be linked with the away team’s impaired shooting accuracy (i.e., movement precision) and rebounding, which may be separately influenced by either circadian disruption or the general effect of travel, as these differences manifest differently when teams travel within or across multiple time zones.