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The Sports Bubble Advantage

Playoffs are the best of times and the worst of times... at least if you are a fan of the National Basketball League (NBA) or the National Hockey League (NHL). It’s that magical time of the year where champions are crowned, and hearts are broken. Where the hardiest of players play harder, the fastest are faster, and the skillful dazzle like diamonds under the crushing pressure of expectations. It’s the playoffs. Whether your team is carrying on to the next round or you’re rooting against a rival, nothing feels more exciting than a win or feels more upsetting than a loss.

The road to the playoffs is a long and arduous endeavor. In a normal season, both NBA and NHL teams pack 82 games, countless practices, and thousands of miles of travel into the six months between October and April. The primary goal of the regular season is to place high enough within the top of the conference standings to continue on for another two months of playoff action and a shot at becoming the league champion. For teams who are a shoo-in for the playoffs, the regular season is about jockeying for top spots within those standings to secure that one extra game of home advantage.


Fans play an important role in a team’s success. Fans show up to games wearing their team’s logos and colors. You cheer “Let’s Go!” louder than the other guys wearing those other stupid colors and that dumb logo. You boo louder than they do too. And you boo the refs for good measure (sometimes…it depends on the call). As a matter of fact, your team wins 55% of the time you wear your lucky game day socks and that is slightly better than chance (so why chance not wearing them, even if they aren’t “clean”?). You’re the home team, and those other guys are in YOUR HOUSE. You won’t let them forget it. Your team surely has the home advantage as long as they are playing home, right?


But what really is a “home advantage,” and why is it considered to be so important? Do professional sports teams benefit from playing in their hometown or is it that visiting teams have a slight disadvantage by playing on the road? Is it you, the fan, that makes the difference, or is there something else going on?


Home Advantage

It is a fairly well-known phenomenon in professional sports that teams playing in their home arena tend to win more games on average (1). This phenomenon, known as home advantage, has been widely studied by scientists for decades. Early research that showed the existence of home advantage also indicated that home advantage is most prominent in team-based indoor sports, such as basketball and ice hockey(1). Some research has pointed to a variety of factors that have an influence on the eventual outcome. The two most prominent of these factors are home crowds/crowd size and travel, especially across time zones (2). However, more recent evidence suggests that travel and home city familiarity plays a much larger role than the crowd, showing little support that the crowd effect is a key contributor to the end result of a match (3).


The Effects of Travel

If you’ve ever travelled large distances, you may have a little sympathy for professional athletes who make a living going from town to town to perform. Sure, professional athletes don’t have to stand in line for two hours to get through TSA, lug their overstuffed bag 10,000 steps to the last gate in the terminal, and then squeeze into their middle seat between two large strangers. However, they do have to deal with long late-night flights, time away from their families, and unfamiliar hotel rooms with roommates who may not have the same sleep schedule. All of these things are possible contributors to sleep impairment, fatigue, and other mind/body-related performance issues (4). Further, long-distance travel across multiple time zones can have a major effect on the natural circadian cycle of an athlete (5). Until acclimated to the new time zone, the athlete could experience lulls in their alertness and a hindrance in their performance.


Lack of Travel and the Bubble

Given the circumstances of the COVID-19 pandemic, the NBA and the NHL created “bubbles” in which teams could compete in their respective playoffs in an environment that was closed off from in-person crowds-- a single hub that was cohabitated by opposing teams similar to an Olympic village. In scientific terms, this was a near-perfect control to remove the home advantage factors of travel.


Of the big four professional United States sports, the NBA and the NHL instituted a more restrictive bubble than Major League Baseball (MLB) and the National Football League (NFL), the main restriction being travel. According to a study by Nico Higgs and Ian Staveness (6), which compared home advantage in the bubble by using a Bayesian framework to determine a team’s relative strength against opponents, the NBA and the NHL had a more pronounced decrease in home team advantage in the bubble than the NFL and MLB which continued to travel through the pandemic. This indicates that travel and city familiarity may play a larger role in home advantage than crowd and crowd size, since in-person crowds were not allowed at any of the NBA, NHL, or MLB games and the majority of NFL games (although the same teams allowed small socially distanced crowds in their massive stadiums).


Additionally, a study by Andrew W. McHill and Evan D. Chinoy (7) examined the NBA bubble effects on not only the final matchup result but a breakdown of the key performance stats that influenced those outcomes. Their examination showed that pre-bubble travel impaired an away team’s shooting accuracy, rebounding, and winning percentage. Further, they showed that home advantage provided an increase in points scored by the home team. These home team advantage factors were nearly eliminated in the bubble.


Future Research

The professional sports bubble in 2020 created a great opportunity for researchers and sports enthusiasts alike to examine what it is that gives teams an edge in a controlled environment vs pre (and now post) bubble environments. Given the advanced statistics available for all of the major sports as well as the introduction of new tracking technologies within the sports, there is trove of performance data waiting to be analyzed, broken down, and understood. Aspects of athletic performance include reaction time, which is also the basis of performance predictions in SAFTE-FAST. Task Effectiveness in SAFTE-FAST is based on reaction time from a laboratory test—the Psychomotor Vigilance Task (PVT) and scaled to 100% of an average person’s normal best performance. SAFTE-FAST is used to assess performance in other highly-skilled individuals who travel long distances for work—pilots—so it may be that SAFTE-FAST could be adapted for performance prediction in athletes as well. While our science team does not have any concrete plans to predict athletic reaction times with SAFTE-FAST, given the amount of free data available in the sports world, it would not be difficult to do retrospective analysis. Athletes may not work in a safety-sensitive industry, but they encounter many of the same fatigue factors important in operational environments. Studying the effects of travel on athletic performance may also help us learn more about the effects of travel on operational performance. After all, while playing at home may give your team more of an advantage over the travel-weary visiting team than you chanting “Let’s Go” from the nosebleed section, the science is still out on your lucky game day socks.


References

1. Schwartz, B, Barsky, SF. The Home Advantage. Social Forces. 1977; 55(3): 641–661. https://doi.org/10.2307/2577461.

2. Nevill, AM, Holder, RL. Home Advantage in Sport. Sports Med. 1999. 28: 221–236. https://doi.org/10.2165/00007256-199928040-00001.

3. Pollard, R, Pollard,G. Long-term trends in home advantage in professional team sports in North America and England (1876 – 2003). Journal of Sports Sciences. 2005. 23:4: 337-350, DOI: 10.1080/02640410400021559.

4. Huyghe, T, Scanlan, AT, Dalbo, VJ, Calleja-González, J. The negative influence of air travel on health and performance in the National Basketball Association: a narrative review. Sports (Basel). 2018. 6(3):89. doi: 10.3390/sports6030089.

5. Song, A, Severini, T, Allada, R. How jet lag impairs Major League Baseball performance. Proceedings of the National Academy of Sciences. 2017. 114(6): 1407–1412. https://doi.org/10.1073/pnas.1608847114

6. Higgs N, Stavness I. Bayesian analysis of home advantage in North American professional sports before and during COVID-19. Sci Rep. 2021. 11(1):14521. doi: 10.1038/s41598-021-93533-w.

7. McHill, AW, Chinoy, ED. Utilizing the National Basketball Association’s COVID-19 restart “bubble” to uncover the impact of travel and circadian disruption on athletic performance. Sci Rep. 2020. 10: 21827. https://doi.org/10.1038/s41598-020-78901-2