When DSC Arminia Bielefeld scored in the 2025 DFB Cup Final, fans in the stadium saw their heart rates spike by up to 36%—a jolt of joy captured not by cheers, but by data. Now, researchers at Bielefeld University are scaling that insight globally with the Football Fever Study, now open to fans wearing any of 13 major smartwatch brands during the 2026 FIFA World Cup. What began as a Garmin-only project on May 28 has rapidly expanded to include Apple Watch, Samsung Health, Fitbit, Oura, Polar, and others, turning millions of fans into potential citizen scientists.
The study taps into a powerful, underused resource: the biometrics quietly collected on wrists around the world. By analyzing heart rate, stress levels, movement, and sleep patterns, the research team aims to understand how football’s emotional rollercoaster affects the body in real time. “We want to include as many fans as possible, regardless of the nation they support and the smartwatch they wear,” says Professor Dr. Christian Deutscher, co-project leader at Bielefeld University’s Faculty of Psychology and Sports Science. “More participants lead to more robust data, and that increases the study’s explanatory power.”
With national loyalties running deep, the team is especially eager to hear from fans in Eastern and Southern Europe and Turkey, whose voices are currently underrepresented in the dataset. But no matchday commitment is too small. “Anyone who wants to watch a few matches can still take part,” adds Professor Dr. Christiane Fuchs, head of the Data Science group at the Faculty of Business Administration and Economics. “Even individual games give us valuable data.”
All data are collected anonymously and in line with strict data protection standards, ensuring privacy while enabling rich analysis. The study is hosted under Bielefeld University’s Focus Area QUAMU, which specializes in the quantification of uncertainty, and runs in collaboration with the university’s Wissenswerkstadt (Knowledge Hub). Initial findings—such as the stark contrast between in-stadium fans (average heart rate: 94 bpm) and TV viewers (79 bpm) during the 2025 DFB Cup Final—are already pointing to the physical intensity of fandom. These insights could reshape how we understand emotional stress, sports psychology, and even urban planning around major events.
As the 2026 World Cup unfolds, the team plans to share preliminary results on their website, with special attention to matches involving the German national team. But the ultimate goal extends beyond one tournament. By building the largest-ever dataset on fan physiology, the Football Fever Study could offer lasting insights into how collective emotion moves through bodies and communities—measured, one heartbeat at a time.