Altitude and Sport
Introduction[edit | edit source]
With an increase in altitude, there is a decrease in atmospheric pressure, the partial pressure of oxygen, air temperature and air density. These features influence an athlete's performance in different ways. For example, the decrease in air density at altitude offers less resistance to high-speed movements; it has been shown that sprint performances are either not affected by altitude or improve at altitude.
Characteristics of Altitude Ranges[edit | edit source]
Definitions and characteristics of altitude ranges include:
- Sea level (0 to 500 m)
- near to sea level
- no adverse effects
- Low altitude (500 to 2000 m)
- no effects on well-being
- performance may be decreased, but easily restored by acclimation
- Moderate altitude (2000 to 3000 m)
- risk for adverse effects if not acclimated
- acclimation is important for performance
- performance and aerobic capacity decreased
- performance may or may not be restored by acclimation
- mountain sickness may start to occur
- High altitude (3000 to 5500 m)
- risk of acute mountain sickness becomes clinically relevant
- performance is impaired and not restored by acclimation
- Extreme high altitude (above 5500 m)
- risk of severe hypoxic effects
- prolonged exposure leads to progressive clinical deterioration
In sports medicine, high altitude is considered anything greater than 1500 m.
Effect of Altitude on Atmospheric Pressure[edit | edit source]
- Atmospheric air is a mixture of gases. Each gas independently contributes to the total atmospheric pressure (Dalton's law = the total atmospheric pressure is equal to the sum of the partial pressures of the individual gases in the air).
- The pressure exerted by each individual gas is known as the partial pressure.
- Atmospheric pressure = a measure of the weight of a column of air directly over a specific spot.
- Sea level (0 m) = height and weight of column of air is the greatest; atmospheric pressure = 760 mmHg.
- Mount Everest (8848 m) atmospheric pressure = 250 mmHg.
- Increase in altitude (as a person goes higher) - the height and weight of the column of air are reduced, thus atmospheric pressure decreases with increasing altitude. The air is less dense and there is a lower concentration of gas molecules.
- Atmospheric pressure varies, but air composition (percentages of gases in the air) does not. The composition of air is made up of:
- oxygen (20.93%)
- partial pressure of oxygen (PO2) at sea level = 159 mmHg (20.93% of 760 mmHg)
- partial pressure of oxygen on Mount Everest = 52 mmHg (20.93% of 250 mmHg)
- carbon dioxide (0.3%)
- nitrogen (79.04%)
- oxygen (20.93%)
- Any changes in the partial pressure of each gas is due to changes in atmospheric or barometric pressure.
- The decrease in partial pressure of oxygen with an increase in altitude has a direct effect on saturation levels and an influence on oxygen transport.
- At altitude, the partial pressure of oxygen is low in the lungs. The partial oxygen gradients between the alveoli and lungs and the blood where the oxygen is loaded, as well as between the blood and tissue where the oxygen is unloaded are decreased.
Effect of Altitude On Temperature and Humidity[edit | edit source]
- Air temperature
- cold air holds very little water
- air at altitude is very cold and very dry
- dry air leads to quick dehydration via the skin and lungs
- cold and dry air combined increase the risk of cold-related disorders and dehydration
Effect of Altitude on Other Aspects[edit | edit source]
- Solar radiation increases as altitude increases
- Ultraviolet radiation increases as altitude increases
- Water normally absorbs the sun's radiation - as altitude increases, there is a decrease in water vapour which results in less absorption
- Snow / ice reflects and amplifies solar radiation
Physiological Responses to Acute Altitude Exposure[edit | edit source]
Hypoxaemia = low oxygen in blood levels
Hypoxia = low levels of oxygen in tissue
When an athlete is exposed to altitude, acute hypoxia occurs and the body responds as follows:
Respiratory System[edit | edit source]
- Increase in ventilation at rest and submaximal exercise
- Peripheral chemoreceptors in the aortic arch and carotids are stimulated by the decrease in arterial partial pressure of oxygen (PaO2)
- Increase in ventilation is associated with an increase in tidal volume
- Respiratory alkalosis occurs as a result of increased "blowing off" of carbon dioxide (CO2)
- Diffusion of oxygen from the alveoli to arterial blood = pulmonary diffusion
- Altitude does not limit gas exchange between the alveoli and blood, thus alveolar PaO2 is still similar to capillary PaO2
- Hypoxaemia (low arterial blood PaO2) is a direct reflection of low alveolar PaO2
- At altitude, the alveolar PO2 decreases and, thus, there is less haemoglobin saturation
Gas Exchange at Muscles
- At sea level, the pressure gradient between arterial PaO2 (100 mmHg) and tissue PaO2 (40 mmHg) is 60 mmHg
- At altitude (for example 4300 m), the pressure gradient between arterial PaO2 (42 mmHg) and tissue PaO2 (27 mmHg) is 15 mmHg
- This is a significant reduction in the diffusion gradient of oxygen
- This change in diffusion gradient has a greater impact on exercise performance than the reduction in haemoglobin saturation in the lungs
Figure 1 compares the partial pressure of oxygen (PO2) in inspired air and body tissue at sea level and at altitude. As the inspired partial pressure of oxygen decreases, so does the alveolar partial pressure. The arterial partial pressure of oxygen is similar to the partial pressure in the lungs, but the diffusion gradient of oxygen diffusion into tissue such as muscle is significantly reduced.
Cardiovascular System[edit | edit source]
- Decrease in plasma volume within the first few hours at altitude:
- result of respiratory water loss and increase in urine production
- leads to an increase in the haematocrit (percentage of the blood volume made up of red blood cells, containing haemoglobin), resulting in more red blood cells for any given blood flow and more oxygen being delivered to tissue for a given cardiac output
- Plasma volume returns to normal after a few weeks at altitude if enough fluids are taken
- When an athlete is continuously exposed to altitude, it triggers the kidneys to release erythropoietin (EPO)
- erythropoietin is a hormone that stimulates red blood cell production
- the total number of red blood cells is increased and this helps the athlete compensate for the lower partial pressure of oxygen experienced at altitude
- this is a slow process, taking weeks to months
- Increased cardiac output at rest and submaximal exercise
- Cardiac output = stroke volume x heart rate
- stroke volume decreases with the decrease in blood volume
- heart rate increases at rest and submaximal exercise, brought on by an increase in sympathetic nervous system activity
- this is a short-term adaptation and after 6 to 10 days at altitude, cardiac output and heart rate during any given exercise bout will start to decrease
Consequences of Acute Altitude Exposure[edit | edit source]
- exaggerated fluid loss at altitude through the skin, respiratory system and kidneys, and sweating with exercise
- zthletes should consume 3 to 5 litres of fluid per day and fluid intake should be tailored according to the athlete's needs
- Decreased appetite
- in combination with increased metabolic rates at altitude, this can lead to energy deficits of up to 500 kcal/ day and weight loss
- athletes should be educated about adequate nutrition at altitude to support their activities and performance
- iron-rich foods and iron supplements may be necessary to support the increase in red blood cell production
- Maximal oxygen consumption (VO2max) decreases as altitude increases - this generally happens at altitudes of 1500 m and above
- decreased VO2max due to the decrease in arterial PO2 and decreased maximal cardiac output
- decrease in VO2max of 8 to 11 percent for every 1000 m ascent
- Aerobic exercise performance is affected the most by the hypoxic conditions at altitude (endurance events are impaired at altitude)
- VO2max decreases as a percentage of sea level VO2max as an athlete ascends
- this limits exercise capacity
- athletes with a higher VO2max and aerobic capacity at sea level will be able to complete a standard task with less perceived effort and less cardiovascular and respiratory stress at altitude than athletes with a lower VO2max at sea level. Therefore, if everything else is equal, an athlete with a high VO2max at sea level will have an advantage at altitude.
- Moderate altitude does not affect anaerobic performance such as 100 m to 400 m track sprints
- these events have minimal oxygen requirements and the energy for these events is provided by the adenosine triphosphate - phosphocreatine (ATP - PCr) and anaerobic glycolytic systems
- Thinner air at altitude provides less air resistance to movements and may lead to improved swim and run times (up to 800 m) and jump distances (long jump, triple jump). Varied effects have been noted in throwing events such as shot put and discus performance.
Acclimation to Altitude[edit | edit source]
- Acclimation = short-term adaptations to altitude in terms of chronic exposure to altitude
- Acclimation to altitude improves performance, but the performance may never match the athlete's performance at sea level
Chronic Exposure to Altitude - Acclimatisation[edit | edit source]
The following refers to more extended periods of exposure (such as weeks or months) to altitude:
- Erythropoietin (EPO) concentration increases for 2 to 3 days after altitude exposure
- Polycythaemia (increased red blood cells) stimulated by EPO release
- This elevated red blood cell count can be evident for 3 months or more
- Consequences of polycythaemia
- at sea level, the average haematocrit (percentage of total blood volume composed of erythrocytes) is around 45 percent
- at altitudes of 45oo m, the average haematocrit is about 60 percent
- blood's haemoglobin content increases proportionally with the increase in altitude
- Plasma volume decreases initially with acute altitude exposure, but over time it increases
- Structural changes to muscle
- decrease in cross-sectional area
- increase in capillary density
- Reduced metabolic potential of muscle
- mitochondrial function and glycolytic enzyme activity reduced after four weeks at altitude
- reduced oxidative capacity
Training and Performance[edit | edit source]
- At altitude, high-intensity aerobic training is prevented by hypoxia (an athlete can't work as hard as at sea level).
- Living high, and training high can cause dehydration, low blood volume and decreased muscle mass, and the literature shows poor validation of altitude training for sea-level performance.
- Sea level athletes competing at altitude have two options:
- they should compete as soon as possible (within 24 hours) after arrival at altitude. Although this does not confer the benefits of acclimation, the exposure to altitude is brief enough that the adverse effects of altitude are minimal or less.
- athletes should train at altitude for a minimum of two weeks before competing as the worst adverse effects of altitude will have dissipated
- Live high, train low seems to be the best of both worlds as this allows for passive acclimation to altitude and training intensity is not compromised by a low partial pressure of oxygen.
Health Risks of Acute Altitude Exposure[edit | edit source]
- Acute mountain sickness (AMS)
- onset 6 to 48 hours after arrival at altitude, most severe on days 2 and 3
- nausea / vomiting
- can be avoided by a slow, gradual ascent to altitude and climbing no more than 300 m per day at altitudes above 3000 m.
- read more: Acute mountain sickness
- High-altitude pulmonary oedema
- accumulation of fluids in the lungs
- a life-threatening condition
- related to hypoxic pulmonary vasoconstriction as a result of hypoxia - this causes clot formation in the pulmonary circulation
- shortness of breath
- persistent cough
- chest tightness
- excessive fatigue
- the disruption of breathing can lead to:
- decreased oxygenation of the blood
- supplemental oxygen
- immediate descent to a lower altitude
- High-altitude cerebral oedema
- accumulation of fluid in the cranial cavity
- complication of high-altitude pulmonary oedema
- life-threatening condition
- most cases reported at altitudes greater than 4300 m
- supplemental oxygen
- hyperbaric bags
- immediate descent to lower altitude
Resources[edit | edit source]
References[edit | edit source]
- Bergeron MF, Bahr R, Bärtsch P, Bourdon L, Calbet JA, Carlsen KH, Castagna O, González-Alonso J, Lundby C, Maughan RJ, Millet G. International Olympic Committee consensus statement on thermoregulatory and altitude challenges for high-level athletes. British journal of sports medicine. 2012 Sep 1;46(11):770-9.
- Laskin, J. Altitude as Environmental Concern in Sport Course. Plus. 2023
- Powers, Scott K. Howley, Edward T. editors. Exercise and the Environment. Exercise Physiology - Theory and Application to Exercise and Performance. 10th Ed. New York: McGraw-Hill Education. 2018. p548-572
- Kenney WL, Wilmore JH, Costill DL. Exercise at Altitude in Physiology of sport and exercise. Human kinetics; 2021 Oct 26.
- Carceller A, Javierre C, Ríos M, Viscor G. Amputation risk factors in severely frostbitten patients. International journal of environmental research and public health. 2019 Apr;16(8):1351.
- Dhillon S. Part B–High Altitude. Conflict and Catastrophe Medicine: A Practical Guide. 2009 Apr 2:114.
- Rastogi A, Yadav S, Kumari P, Sinha RK. UV-B and Its Climatology. InUV-B Radiation and Crop Growth 2023 Jan 1 (pp. 13-21). Singapore: Springer Nature Singapore.
- Gilaberte Y, Trullas C, Granger C, de Troya-Martín M. Photoprotection in outdoor sports: a review of the literature and recommendations to reduce risk among athletes. Dermatology and Therapy. 2022 Feb;12(2):329-43.
- Sharma KP. Temporary hypoxemia at high altitude in an intensive care unit physician. SAGE Open Medical Case Reports. 2023 Feb;11:2050313X231153526.
- Schüttler D, Weckbach LT, Hamm W, Maier F, Kassem S, Schier J, Lackermair K, Brunner S. Effect of acute altitude exposure on ventilatory thresholds in recreational athletes. Respiratory Physiology & Neurobiology. 2021 Nov 1;293:103723.
- Viscor G, Corominas J, Carceller A. Nutrition and Hydration for High-Altitude Alpinism: A Narrative Review. International Journal of Environmental Research and Public Health. 2023 Feb 11;20(4):3186.
- Byte Size Med. Respiratory Response To High Altitude | Acclimatization Physiology | Respiratory Physiology. Available from: https://www.youtube.com/watch?v=6KHQGS4jJyI [last accessed 27/02/2023]
- Roche J, Rasmussen P, Gatterer H, Roveri G, Turner R, van Hall G, Maillard M, Walzl A, Kob M, Strapazzon G, Goetze JP. Hypoxia briefly increases diuresis but reduces plasma volume by fluid redistribution in women. American Journal of Physiology-Heart and Circulatory Physiology. 2022 Dec 1;323(6):H1068-79.
- Mairbäurl H. Kinetics of changes in haemoglobin after ascent to and return from high altitude. Journal of Science in Sport and Exercise. 2020 Feb;2(1):7-14.
- Palubiski LM, O'Halloran KD, O'Neill J. Renal physiological adaptation to high altitude: A systematic review. Frontiers in physiology. 2020 Jul 16;11:756.
- Williams AM, Levine BD, Stembridge M. A change of heart: Mechanisms of cardiac adaptation to acute and chronic hypoxia. The Journal of physiology. 2022 Sep;600(18):4089-104.
- Amber Ziebarth. Cardiovascular Effects of Altitude Training. Available from: https://www.youtube.com/watch?v=3_2epU7LOcg [last accessed 27/02/2023]
- Girard O, Brocherie F, Millet GP. Effects of altitude/hypoxia on single-and multiple-sprint performance: a comprehensive review. Sports medicine. 2017 Oct;47:1931-49.
- Global Triathlon Network. Altitude Training: Why The World's Best Athletes Do It! Available from: https://www.youtube.com/watch?v=qTHGPLP_v_Y[last accessed 27/2/2023]
- NN Running Team. Documentary | The importance of altitude for athletes. Available from: https://www.youtube.com/watch?v=Ch7wEnci1J4 [last accessed 27/02/2023]
- Mallet RT, Burtscher J, Pialoux V, Pasha Q, Ahmad Y, Millet GP, Burtscher M. Molecular Mechanisms of High-Altitude Acclimatization. International Journal of Molecular Sciences. 2023 Jan 15;24(2):1698.