Time zones and tiredness strongly influence NBA results, study of 25,000 matches shows

The authors say their findings, from more than 25,000 matches, show elite basketball coaches and teams should consider the physical and mental effects of time zone travel when planning games and preparing for games.

A first of its kind, the research is based on the achievements at home and away of NBA (National Basketball Association) league players across 21 consecutive seasons. Considered the most competitive in the world, NBA athletes frequently travel to matches across the five US time zones used by NBA teams.

The findings show that there is a near 10% better win ratio difference for home teams from the western time zone area (PDT) when playing against a team from the eastern EDT time zone, compared to when an EDT team hosts a PDT team.

• When PDT teams play at home against EDT teams the winning percentage is 63.5%.
• When EDT teams host a PDT team, the winning percentage drops to 55.0%.

In addition, the findings also show that teams win more home games when players' sleep-wake cycles -- linked to their circadian rhythm (CR) -- are 'ahead' of the local time. This is after they have returned west from competing in a city further east where the local time is earlier.

For example, if the LA Lakers play an away match at Miami (EDT) and then return to Los Angeles (PDT) to play a home game without much CR adaptation time (CR is ahead of the local time), the Lakers play the next home game with a CR advantage against whomever their opponents are.

Teams do not have the same success when players' internal body clocks are either behind or synchronized with the local time where their home arena or stadium is based, according to the results.

Experts from Dokuz Eylül University and Yildiz Technical University, in Turkey, led the study. Dr Firat Özdalyan, a Sport Physiology expert from Dokuz Eylül, explains that they found NBA teams need to become used to the local time when they play away games to perform well.

"One of the most important results of this research for the home games of the NBA teams is that while traveling to the west increases the performance, traveling to the east decreases the performance," he states.

"Another notable finding is that the success of NBA teams increases when they are fully adapted to the local time for away games.

"Home teams who will be exposed to such a CR phase shift (traveling from west to east) should be mindful of these potential performance detriments when constructing game plans.

"It can be suggested that coaches (of away teams) should bear this (the low shooting success) in mind during the game preparation period."

A circadian rhythm (CR) is the body's sleep-wake pattern over a 24-hour day. A CR phase shift means bedtime and wake-up times move earlier or later in the day.

This means the body clock gets out of sync with the environment which can lead to sleeplessness, daytime tiredness and other issues. The body clock needs 24 hours to adapt for every one-hour time zone change.

The study investigated the effect of a CR shift on the performance of professional NBA athletes.

Data was analyzed from 25,016 regular games across 21 consecutive seasons between 2000 to 2021. Information included the date, location, game result and home or away team. Time zones of the cities where all games were played were identified to calculate the CR phase shifts of the teams.

The expert team say teams in the Pacific time zone may have an advantage in regular season home games such as the Los Angeles Lakers, Portland Trail Blazers, and Seattle Supersonics.

Anaerobic performance could explain why home teams who travel from east to west do better, say the authors. This type of activity which is crucial for scoring, defending and other feats peaks later in the day.

The authors add that the body clock adapts more easily to a long rather than a short day. The day becomes longer traveling east to west and a natural circadian rhythm is slightly longer than 24 hours. So this means basketball players are traveling in the direction their bodies want to go.

As for away teams, the authors say that travel fatigue is more likely to blame for poor performance than phase shifts in CR.

Players who have rest time between games or have not traveled across time zones for an away match are more able to synchronize their body with the local time. As such, they are not as tired and play better.

A limitation of this research is that the traveling schedules of the teams are not known. Since this information was not available, it was not possible to determine how long the teams stayed in which city/time zone; how much they adapted to the local UTC; and what extent they were exposed to a CR phase shift with real data. Therefore, the team used a predictive model for the traveling plans and CR adaptations of the teams by following the rules determined by previous research.

Another limitation is that the games were not separated according to teams' ability differences.