Ever finish a workout and think, “Why did that feel so hard” even though your watch says you ran your usual pace? A new season-long analysis suggests air pollution can create that exact mismatch for elite women soccer players, even when the usual performance stats barely move.
In a paper published on Nov. 25, 2025, a research group led by Adam Beavan with Ross Julian, Falk Gogolla, Sascha Härtel, and Michael Stephen Koehle tracked training and match data across an entire season. They found that moderate air pollution levels did not clearly reduce distance run, sprinting, or heart rate, but players reported that sessions felt harder on the most polluted days.
A season of soccer data, not a lab test
The study followed a professional women’s team in Hoffenheim, Germany during the season that ran from July 2022 to May 2023, using routine performance tracking already collected by TSG Hoffenheim. The dataset included 27 matches and 180 training sessions, covering more than 2,000 player training observations and more than 300 player match observations.
Researchers also worked with data and oversight connected to the University of Münster, and the ethics review was handled through the University of British Columbia. That matters because it was real-world soccer with real-world variables, not a controlled experiment where everything is kept the same.
What “air pollution” meant in this study
The team focused on three common outdoor pollutants in Germany, PM10 (tiny inhalable particles such as dust and soot), ozone, and nitrogen dioxide. Pollution was described in micrograms per cubic meter, which is a standard way air agencies report how much of a pollutant is in a given volume of air.
Instead of measuring the air directly on the sideline, the researchers used readings from nearby monitoring stations in the German Federal Environment Agency network, also known as the Umweltbundesamt. For matches, the nearest stations were on average about 4 miles away, and the nearest station to the training site was about 5 miles away, with weather conditions pulled from the German Meteorological Service, also called Deutscher Wetterdienst.
Most performance stats did not fall
A lo largo de la temporada, los jugadores entrenaron y compitieron en condiciones de contaminación relativamente bajas o moderadas. En lo que respecta a las partículas PM10 en particular, ninguna de las sesiones se realizó en días con niveles superiores al límite de referencia que la Organización Mundial de la Salud destaca en sus directrices sobre la calidad del aire, y la mayoría de las sesiones se mantuvieron muy por debajo de los niveles que estudios deportivos anteriores han vinculado con descensos más evidentes en el rendimiento.
That helps explain the headline result. When pollution rose and fell, the objective numbers like distance covered, sprint counts, and average heart rate did not show a consistent pattern of getting worse, at least in the range of air quality this team typically experienced.
Effort ratings rose when ozone and nitrogen dioxide were higher
The clearest signal showed up in the athletes’ own reports of how hard the session felt. After training or matches, players rated their effort on a simple 0 to 10 scale called rating of perceived exertion, or RPE.
When a combined pollution measure called “Ox” was high, RPE rose by about 0.8 points in the highest exposure range. In plain terms, the players were not obviously running less, but they felt like they were working harder to do the same job.
What “Ox” is, and why it showed up
Ox is not a separate pollutant you can point to in the air. It is a combined measure that puts ozone and nitrogen dioxide into a single number, aiming to capture the “oxidizing” mix that can irritate airways, especially when breathing gets heavy during intense play.
The study found this combined measure kept popping up in the statistical models, more than the particle measure did. That does not prove cause and effect, but it suggests that for this team’s environment, the gas mix may have been more relevant to how sessions felt than the particle levels they were exposed to.
A possible acclimation effect that complicates the story
One of the more surprising findings was what happened when researchers looked at recent exposure, not just same-day conditions. When they accounted for Ox levels across the previous seven sessions, the negative effect on RPE in the highest pollution range did not just shrink, it flipped direction in the model.
This lines up with earlier work that has hinted at short-term acclimatization to ozone exposure during sport, including a 2018 study in Health Economics that linked ozone to athletic performance while also suggesting recent exposure history can change the impact.
The menstrual cycle question remains open
Because earlier research has suggested women can be more affected by air pollution during exercise, the team also explored whether menstrual cycle phase changed the relationship. They did not find a clear interaction between cycle phase and pollution levels for performance or wellness outcomes.
Still, there is an important catch. Cycle phase was self-reported using a questionnaire based on a theoretical 28-day cycle, not hormone testing, so the phase labels can be off for many people. In other words, the study raises the question in a smart way, but it cannot close the case.
Why this matters beyond one team
For coaches and performance staff, the practical takeaway is that air pollution might show up first in “how it felt,” not in GPS totals. If athletes say a session felt unusually taxing, it may be worth checking air quality alongside the usual suspects like heat, sleep, and training load.
Guidance documents already encourage common-sense steps like monitoring local air conditions, adjusting timing, and reducing exposure near traffic corridors, especially for outdoor endurance work. A 2023 position statement summarizes many of these strategies in athlete-friendly terms.
The main study has been published in Frontiers in Sports and Active Living.
