Exercising at a higher altitude than usual can be a fantastic experience , but it can also place additional demands on the body. The higher the altitude, the lower the oxygen availability and the greater the effort required to perform the same physical activity. Altitude can affect anyone engaging in mountain hiking, cycling, running, skiing, or other sports at high elevations, especially above 2,500 meters and when ascent is rapid. What changes in the air and the body at altitude? Although the percentage of oxygen in the air remains approximately 21%, the reduction in atmospheric pressure lowers the partial pressure of oxygen . In practical terms, less oxygen is available to pass from the lungs into the bloodstream and reach the muscles and other organs. To compensate for the reduced oxygen availability, the body immediately begins to adapt: Breathing rate and depth increase; Heart rate increases, particularly during exercise; Over the following days, additional adaptations develop to improve oxygen transport and use; With more prolonged exposure, the production of red blood cells may gradually increase. Activities that can normally be performed easily at low altitudes may require significantly greater effort at higher elevations. After a rapid ascent, some people may experience headaches, nausea, dizziness, unusual fatigue, loss of appetite, or difficulty sleeping. These symptoms may be consistent with acute mountain sickness, especially when they occur above 2,500 meters. Shortness of breath at rest, persistent cough, rapidly worsening symptoms, confusion, marked drowsiness, or difficulty walking in a coordinated manner are warning signs that require stopping the ascent, descending, and seeking urgent medical assessment. The risk of altitude-related problems increases with elevation , particularly above 2,000-2,500 meters, and with the speed of ascent. Better physical fitness and extensive mountain experience do not prevent altitude sickness from occurring. In which situations is it more common? Altitude-related problems may occur with any sport at altitude, including: Mountain running; Cycling in mountainous regions; Climbing and mountaineering; Skiing and snowboarding; Training sessions of any sport performed at high elevations; Sporting competitions at significant altitude. However, there are important differences between professional athletes and recreational participants. Professional or elite athletes usually plan their acclimatization, adjust their training load, and monitor their individual response before training or competing at altitude. Recreational participants often have fewer days available for gradual adaptation and may begin exercising shortly after arrival. When ascent is rapid and initial exertion is intense, the risk of symptoms increases. Good physical fitness does not eliminate this risk. Precautions for anyone exercising at altitude If you exercise and plan to do so at altitude, several measures can help reduce the risk of problems: Ascend gradually Whenever possible, spend one night at an intermediate altitude before ascending further. Above 3,000 metres, the sleeping altitude should generally not increase by more than about 500 metres per day, including a rest day without further ascent every three or four days. Reduce initial intensity During the first few days, exercise at a lower intensity than usual and gradually increase the workload according to your body's response. Maintain adequate hydration Dry air and increased ventilation can promote fluid loss. Drink according to thirst, exercise intensity, temperature, and observed fluid losses, avoiding both dehydration and excessive water intake. Overhydration does not prevent altitude sickness. Maintain adequate diet Insufficient energy and nutrient intake may worsen fatigue and impair recovery, particularly during prolonged activities. Monitor symptoms carefully If you develop headaches, nausea, dizziness, or unusual fatigue, stop intense exercise and do not continue ascending while symptoms persist. If symptoms do not improve with rest or if they worsen, descend and seek medical advice. Shortness of breath at rest, confusion, loss of coordination, persistent cough, or inability to continue are warning signs that require descent and urgent medical attention. Summer sports Summer sports in mountainous areas may present additional challenges , including higher temperatures and stronger ultraviolet radiation, because the atmosphere filters less solar radiation at altitude. In these situations, the following precautions are recommended: Apply sunscreen regularly to exposed skin; Wear appropriate protective clothing, including a hat and sunglasses; Avoid exercising during the hottest hours of the day. Winter sports In winter sports, cold exposure becomes the main additional challenge , increasing the risk of hypothermia and frostbite. Therefore, it is essential to: Wear layered clothing; Protect hands, feet, and face adequately; Avoid remaining inactive for extended periods. What about non-athletes? These precautions are not only for people engaging in physical exercise. Visitors travelling to mountainous regions for sightseeing and leisure may also experience the effects of altitude. For this reason, it is advisable to: Avoid strenuous activities during the first few days; Maintain good hydration; Protect yourself from cold and sun exposure (depending on the season); Be alert to symptoms such as headaches, dizziness, or excessive fatigue. People with heart or respiratory disease, significant anemia, a history of severe altitude illness, or other medical conditions that may limit exercise tolerance should consult a doctor before travelling to high altitudes. This assessment is particularly important when rapid ascent or vigorous physical activity is planned. In short Altitude does not prevent physical activity , but it requires appropriate progression and sufficient time for the body to acclimatize. Professional athletes usually benefit from structured acclimatization programs , including training-load adjustments and monitoring of individual responses. Recreational participants, who often have less time available for gradual acclimatization, should reduce their initial exercise intensity, avoid excessively rapid ascents, and pay close attention to the development of symptoms. Regardless of experience level, gradual ascent, appropriate adjustment of exercise intensity, adequate hydration, and recognition of warning signs are essential measures for exercising safely at altitude. At the Hospital da Luz Sports Medicine Centre , you can obtain expert advice and support in preparing for exercise and sports activities at altitude. Source Luks AM, Auerbach PS, Freer L, et al. Wilderness medical society clinical practice guidelines for the prevention and treatment of acute altitude illness: 2019 update . Wilderness Environ Med 2019;30:S3-S18. Bärtsch P, Swenson ER. Clinical practice: Acute high-altitude illnesses . N Engl J Med 2013;368:2294-302. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item. English translation generated with AI and reviewed by the editorial team
