Investigation of the effect of circadian rhythm on the performances of NBA teams

Professional athletes competing in the NBA are frequently exposed to time-zone-shifting travels. These time zone changes may cause circadian rhythm (CR) phase shifts and these shifts affect sportive performance. The aim of this study was to investigate the effects of CR phase shifts on the performance of NBA teams. 25,016 regular season games across 21 consecutive seasons were included in the CR phase shift calculations. To examine the CR phase shift effect on team performance, teams were divided into three groups according to local clock: the same internal clock as the local clock (LS); the internal clock ahead of the local clock (LA); and the internal clock behind the local clock (LB). Furthermore, another grouping approach was performed according to opponents' internal clock: the same internal clock as the opponent (OS); the internal clock ahead of the opponent's internal clock (OA); and the internal clock behind the opponent's internal clock (LB). The analyses were performed for all games and for only 19:00-19:30 games separately. 24,985 game data were used to compare these groups in terms of 25 basketball in-game performance metrics. Statistical analyses were conducted separately for home and away teams. For home games, it was found that LA and OA are the most successful groups for all conditions. For away games, it was determined that LS is the most advantageous group. However, none of the OA, OS, and OB groups showed an obvious CR advantage among others. These results revealed that teams from more west may have a CR advantage in regular season home games. However, it is thought that the performance of away teams depends more on travel fatigue than CR phase shifts. Finally, the most important feature of this study is its unique methodological approaches. Hence it is thought that these methods will guide future studies and will be used frequently in the field of exercise physiology.