PUB - Publikationen an der Universität Bielefeld

While the birthday effect has been widely studied in the economics and sport literature, this study introduces the concept of the 'real' birthday effect. It holds that birthday celebrations yield fatigue, which negatively affect running performance. The purpose of this study is to examine the effect of players' birthdays on post-birthday running performance using data from the German Football Bundesliga (2011-2018). The dataset includes 1,040 different field players who played in 2,142 matches (n= 49,233). Running performance was measured by the total distance covered during the game (in m per minute) and the number of intensive runs (>20 and <24 km/h; per minute). On average, players ran 123.68 m and performed 0.70 intensive runs per minute, which are equivalent to 11.1 km and 63 intensive runs during a 90-minute match. The results of fixed effects panel regression analyses, which also control for various player, game, and team characteristics, show that players perform significantly fewer intensive runs on the day following their birthday. This finding supports the concept of the 'real' birthday effect. Football coaches should reconsider fielding players on match days succeeding their birthday as these players perform significantly fewer intensive runs.