Greater circadian disadvantage during evening games for the National Basketball Association (NBA), National Hockey League (NHL) and National Football League (NFL) teams travelling westward
In the same way that home field advantage influences the probability of success (Courneya and Carron, 1992), accumulating evidence suggests that there seems to be a circadian advantage in major sport leagues for teams travelling eastward and a circadian disadvantage for teams travelling westward because of the time zone changes, which impacts the alignment between the scheduled game times and the circadian peak in performance (Jehue et al., 1993; Smith et al., 1997, 2013; Winter et al., 2009). However, these studies have mostly focused on one sport, primarily American football or baseball. Also, most studies have investigated the influence of extreme time zone changes (six time zones or more) on performance (Reilly et al., 2005). However, in professional sport leagues in North America, time zone changes happen on a smaller scale (three time zones or less), but are frequent (sometimes two or three time zones in 1 week). Indeed, in North America, there are four time zones: Pacific Standard Time, Mountain Standard Time, Central Standard Time, and Eastern Standard Time (Winter et al., 2009). It is interesting to note that in recent years, following the increasing evidence of the circadian disadvantage in sport, some efforts have been made to minimize the negative effects of time zone changes. Prevention, such as an increase in awareness regarding the importance of sleep and circadian factors in sport performance, is now promoted among athletes (Erren et al., 2014). On a larger scale, in 2013 for example, the National Hockey League (NHL) proposed a realignment of the league in order to provide each team with the ability to play the majority of their games against teams in the same time zone.
Here we examined regular season games over the past 5 years in three major professional sports leagues in North America: the National Basketball Association (NBA), the NHL and the National Football League (NFL). We hypothesized that there would be a significant advantage for teams playing closer to their circadian peak, which occurs normally in the late afternoon between 15:00 hours and 18:00 hours.