When footballers take to the pitch in sweltering summer conditions, fans often notice the sweat-drenched jerseys, the hands on hips, and the slower pace of play. But what exactly happens to performance when the mercury climbs? A new study led by Edgar Schwarz from Saarland University has put this question under the microscope, analysing more than 1600 professional matches across Europe and Asia.
The findings, published in the International Journal of Sports Physiology and Performance, reveal a striking pattern. As temperatures rise, football players cover less ground, complete fewer high-speed runs, and attempt fewer sprints. The drop-off is measurable and significant, with performance losses becoming more pronounced in hotter conditions. Yet intriguingly, the study also found that peak speeds occasionally climbed higher in warm weather, suggesting that heat reshapes not only endurance but also tactical decisions and physiological responses.
This research does not just interest coaches or fitness analysts. With climate change intensifying heatwaves and major tournaments increasingly scheduled in hot environments, the results matter to players, fans, and football federations worldwide.
Why heat matters in football
The link between temperature and physical exertion is not new. Exercise scientists have long documented how hot and humid conditions disrupt thermoregulation. As the body works harder to dissipate heat, blood flow is diverted to the skin, sweating increases, and cardiovascular strain rises. These changes accelerate fatigue and limit endurance.
In football, where constant running, sprinting, and sudden bursts of acceleration define the modern game, such physiological stress can alter match dynamics. Coaches often stress that high-speed distances and sprinting are more important than total running distance, because they create goal-scoring chances. When these high-intensity actions are curtailed by heat, the outcome of a match can shift dramatically.
Schwarz and his colleagues point out that although experimental trials have demonstrated performance drops in hot conditions, evidence from real-world elite matches was inconsistent. Previous studies were small, scattered, and used varying definitions of what counts as a sprint or a hot match. The new investigation sought to overcome these limitations by drawing on a vast dataset across multiple leagues and treating temperature as a continuous variable rather than splitting it into arbitrary categories.
How the study was conducted
The researchers analysed data from four professional men’s leagues: the German Bundesliga 1 and 2, the Japanese J-League, and the Turkish SüperLig. In total, 1610 matches from the 2021–2022 seasons were included. Each league provided official match statistics collected using optical tracking systems, which allowed precise measurement of distances run, sprint counts, high-speed runs, and maximum recorded speeds.
Crucially, the study linked these performance metrics with environmental data. Two measures of heat were examined. The first was the familiar ambient air temperature. The second was the wet-bulb globe temperature (WBGT), a more sophisticated index that incorporates humidity, wind, and solar radiation to provide a fuller picture of heat stress. Meteorological data were sourced retrospectively from public databases and matched with each game’s location and kick-off time.
By applying linear regression and mixed model analyses, the team quantified how each degree increase in temperature or WBGT influenced player running statistics. This statistical approach avoided crude thresholds and instead revealed a nuanced, near-linear relationship between heat and performance.
The key results
The numbers were clear. Across all leagues, hotter matches were consistently associated with shorter distances covered and fewer sprints. On average, players ran 200 metres less per person for every 10 degrees Celsius increase in WBGT. The number of sprints fell by about one per player per match over the same rise. High-speed running distances also declined, with losses of around 27 metres per player for every 10-degree jump.
In both the Bundesliga and J-League, the effects were particularly strong. German players in the top two divisions ran nearly half a kilometre less per team for each degree increase, while Japanese players showed similar reductions in both total and sprint distances. The Turkish SüperLig displayed weaker associations, though small declines in sprints and high-speed efforts were still observed.
One finding stood out: peak speeds actually increased slightly in hotter conditions. Although total volume of running dropped, the fastest moments became faster. This could reflect physiological changes, since warmer muscles contract more rapidly, allowing bursts of acceleration. It could also suggest tactical pacing, where players conserve energy throughout the game and reserve sprints for the most decisive actions.
Tactical pacing or physiological limits?
The question of why performance declines in heat has two possible answers. The first is physiological. High temperatures compromise the body’s ability to regulate internal heat, pushing heart rate up and hastening fatigue. To protect against heat illness or muscle damage, players simply cannot sustain the same distances.
The second explanation is tactical. Footballers are not robots but decision-makers. They may deliberately reduce their overall running load to conserve energy for key moments. Instead of sprinting repeatedly, they wait for opportunities that matter most, such as chasing down a counter-attack or creating a scoring chance.
The study suggests that both processes likely interact. Players may feel the physiological strain and subconsciously adjust their movements, while teams adopt pacing strategies to balance performance with survival in the heat.
Implications for football science
For clubs, the findings underscore the importance of monitoring heat and adapting preparation. Conditioning staff might shorten warm-ups, employ cooling vests, or rotate substitutions more aggressively during hot games. Sports scientists could tailor training sessions by simulating heat stress, helping players develop resilience.
For federations, the message is equally significant. Match scheduling, hydration breaks, and even stadium design may need rethinking as summers grow hotter. FIFA and UEFA have already faced scrutiny over player safety in extreme climates, particularly during tournaments in countries with high heat and humidity. Evidence like this study strengthens the case for proactive guidelines.
The results also matter for analysts who rely on running statistics to evaluate teams. If performance drops are systematically linked to temperature, comparing metrics across matches without adjusting for climate could be misleading. A player sprinting less in August may not be less fit or committed, but simply coping with environmental stress.
Climate change and the future of football
The research comes at a moment when climate change is reshaping global sport. Heatwaves are more frequent and more intense, affecting everything from grassroots tournaments to the World Cup. In 2022, fans and players alike endured Qatar’s desert climate, where air-conditioned stadiums became controversial symbols of adaptation.
Football is not alone. Tennis has introduced extreme heat policies, athletics schedules have shifted to cooler hours, and cricket has trialled additional breaks. Football, with its vast global following and packed calendar, will face increasing pressure to act.
If temperatures continue to climb, studies like this provide a scientific foundation for change. Evidence that running distances and sprints decline with heat highlights both the risks to player health and the subtle ways the sport itself may evolve.
Global warming is re-shaping outdoor sports. We need to closely monitor these changes to develop evidence based guidelines to ensure the health and safety of athletes around the world.
–Edgar Schwarz
Limitations and unanswered questions
The study, while large, had some constraints. Most matches were played in moderate conditions, with relatively few in extreme heat above 30 degrees. The German leagues, in particular, rarely reached high WBGT values. More research in hotter regions, such as the Middle East or equatorial Africa, could reveal stronger effects.
Another limitation is data standardisation. Each league defines sprints and high-speed runs differently, complicating cross-comparisons. By treating leagues as random effects in their models, the researchers mitigated this issue, but a universal standard would improve future analyses.
Finally, while the statistical associations are robust, they cannot fully separate physiological necessity from tactical choice. Understanding how much of the decline is driven by biology and how much by strategy remains an open question.
Practical applications for players and teams
Despite these caveats, the implications are immediate. Teams can employ cooling strategies, adjust training loads, and plan substitutions more carefully in hot conditions. Coaches may encourage players to conserve energy for decisive phases, while medical staff must remain vigilant for signs of heat stress.
At the organisational level, federations could expand the use of cooling breaks, move matches to evenings, or introduce stricter heat thresholds for postponements. Such measures would not only protect athletes but also sustain the quality of play for spectators.
Perhaps most importantly, clubs and governing bodies must recognise that environmental science is no longer an abstract concern. It is an active factor shaping outcomes on the pitch.
Conclusion
The study by Edgar Schwarz and colleagues from Saarland University, published in the International Journal of Sports Physiology and Performance, offers one of the clearest pictures yet of how rising temperatures affect football performance. Players run less, sprint less, and cover less distance at high speeds when the heat intensifies. Yet within this overall decline lies a curious adaptation, as peak speeds edge higher, reflecting both biological changes and tactical choices.
As climate change accelerates, such insights carry weight far beyond sports science. They remind us that football, like society itself, is not immune to the realities of a warming world. The beautiful game may continue to thrive, but it will do so in an environment where heat is an active opponent.
Reference
Schwarz, E., Duffield, R., Novak, A. R., Görres, T., & Meyer, T. (2024). Associations between match running performance and environmental temperatures in four professional football leagues. International Journal of Sports Physiology and Performance. Advance online publication. https://doi.org/10.1123/ijspp.2024-0248
