Although athletes participating in international competitions such as the World Cup are in optimal physical and athletic condition and mentally prepared to strive for victory, various factors — such as climate changes, altitude, and time zones — that they face during extended travel can trigger changes that affect their performance.

Numerous studies have documented that beyond the track or the playing field, athletes face other “rivals” associated with environmental changes that can manifest as physical and psychological disorders ranging from insomnia, prolonged periods of stress, anxiety, and decreased performance to cardiorespiratory or hormonal disturbances associated with imbalances in the circadian rhythm.

For example, a recent study conducted by specialists from the School of Sport and Health Sciences at Cardiff Metropolitan University in the Cardiff, Wales, and the Faculty of Kinesiology at the University of Split in Split, Croatia, found significant differences in the running performance of professional soccer players associated with variations in the ambient temperature at which matches were played.

The research team used optical tracking devices to collect data from players on 32 teams in the UEFA Champions League(commonly known as the Champions League) in Europe during a total of 125 matches in the 2022–2023 season. This data were classified into four categories based on ambient temperatures during the matches: < 5 °C, 6 °C to 10 °C, 11 °C to 20 °C, and > 21 °C.

The results revealed that physical performance was reduced in matches played at ≥ 21 °C compared with colder conditions. Specifically, total distance covered decreased when the temperature was between 6 °C and 10 °C (d = 0.58). Similarly, high-speed and high-intensity sprints were fewer at ≥ 21 °C compared with matches played at 11 °C to 20 °C (d = 0.54 and 0.43, respectively), 6 °C to 10 °C (d = 0.89 and 0.8, respectively), and ≤ 5 °C (d = 0.62 and 0.57, respectively).

Other studies suggest a decline in high-intensity running performance and players’ cardiac response when ambient temperatures exceed 29 °C, while an analysis of 2014 FIFA World Cup matches found significant reductions in the number of sprints, as well as in the total distance covered by athletes during high-intensity runs, when these actions occurred in high-temperature environments.

With the 2026 World Cup set to take place across Canada, the US, and Mexico during the summer, players will face major environmental risks from heat, air pollution, and high humidity. A scientific report published in Sports Medicine found that 14 of the 16 host cities are expected to experience extreme heat, with historical maximum Wet-Bulb Globe Temperature values ranging from 21 °C to 35 °C and average ambient temperatures between 19.1 °C and 32.7 °C.

When engaging in physical activity in a high-temperature environment, the body’s thermoregulatory system activates mechanisms — such as increased sweating and cutaneous blood flow through vasodilation — to dissipate heat. This can lead to electrolyte imbalances and dehydration, which in turn can damage the heart and reduce the ability to sustain prolonged physical exertion. Furthermore, under high-temperature conditions, metabolic stress increases, leading to faster glycogen depletion and greater reliance on anaerobic energy sources, which could cause any athlete to experience early fatigue.

To prevent these issues, various guidelines have been developed with strategies and recommendations to keep all competitors in optimal health. These guidelines have been adopted by organizations such as FIFA, which introduced three-minute hydration breaks at the halfway point of each half in matches of the 2026 World Cup — a measure that has sparked controversy.

“Sometimes, due to the pace of competition for soccer players, they play up to three matches in a week. To get an idea of the physical strain this entails, keep in mind that they run an average of 10 km per game. If we add training to this, they sometimes end up running more than 50 km a week,” Oswaldo Ballinas Ordóñez, a surgeon specializing in orthopedics, traumatology, and sports medicine, told Medscape’s Spanish edition.

“This is equivalent to running more than one marathon each week; the physical strain is enormous, so it’s important to conduct a battery of functional tests — including cardiorespiratory, muscular, and jumping tests, among others — to closely monitor each player’s health,” he added.

Endocrine Disorders Caused by Circadian Rhythm Disruptions

Ordóñez emphasized that another highly significant factor that can affect the health not only of soccer players but also of athletes in any other discipline with high-performance demands and constant travel involves endocrine and sleep cycle disruptions caused by changes in time zones.

“No matter how demanding your job is, sleeping peacefully in your own bed at home is not the same as constantly leaving your home city and spending much of your time on international trips and travel, staying in hotels and dealing with frequent changes in climate, altitude, and diet. In this regard, soccer players and athletes face a great deal of pressure, so we, as specialists in sports medicine and nutrition, have a lot of work to do to safeguard their health.”

With few exceptions, these aspects are not usually taken into account in sports medicine. “We know that airlines today have excellent aviation medicine programs to safeguard the health of their employees. Competitive athletes may also fly two or more times a week, and the changes in pressure they face not only affect their hormonal balance but also their nutrition. That’s why it’s important to take these situations into account,” he emphasized.

In this regard, a systematic review of the scientific literature focusing on the relationship between sleep, athletic performance, training load, and injuries in soccer players found that, although there were inconsistencies in the findings, some studies suggest that restrictions in the quality and quantity of sleep negatively affect a player’s performance, while increasing the number and severity of musculoskeletal injuries.

On this point, Juan Ricardo López y Taylor, with a specialization in sports medicine and founder of the Institute of Applied Sciences to Physical Activity and Sports at the University Center for Health Sciences of the University of Guadalajara, Guadalajara, Mexico, argued that it is necessary to analyze these types of issues from different perspectives, taking into account both the scientific evidence and the realities faced by athletes, medical teams, and coaching staff on the field.

“If we look at the scientific evidence, the successful management of these situations lies in good planning that begins days before the players board the plane, with the coaching staff adjusting training schedules in advance and controlling the use of melatonin according to the travel route — east to west or vice versa,” the specialist explained.

Additionally, López y Taylor emphasized the need to monitor hydration patterns and maintain a strict sleep schedule, with darkened rooms and no exposure to electronic device screens 1 or 2 hours before bedtime to avoid blocking the natural secretion of melatonin, even resorting to light therapy or light scaffolding when necessary.

Regarding altitude variations, the specialist noted that this is no minor factor when club athletes from coastal areas must travel to locations situated thousands of meters above sea level. At the current World Championship, these differences are notable as host cities like Mexico City and Guadalajara are located at an average altitude of 2240 m and 1570 m above sea level, respectively, while Miami; US; and Vancouver, Canada; are at 1.8 m and 34 m above sea level.

“Coping with these changes requires strategy. In high-performance sports, every detail counts. Therefore, planning for a team’s arrival just 8 hours before the match to mitigate performance loss is crucial and must be done without altering the coach’s tactical approach,” suggested López y Taylor.

Finally, he emphasized that in light of these major challenges — which can similarly affect nonprofessional players, who face even greater risks for injury — “the need to promote short- and long-term scientific research to better understand how the body reacts to all these combined variables is evident.”

“This World Cup, in particular, provides the perfect setting to generate greater knowledge and promote prevention based on evidence. I hope that FIFA will soon share the data and studies (in sports medicine) that emerge from the results of this tournament,” concluded López y Taylor.

Ordóñez and López y Taylor disclosed having no relevant financial relationships.

This story was translated from Medscape’s Spanish edition.