Sea Level to Altitude: How it Impacts Running
For many elite and professional runners, living at altitude (or in an altitude tent) is ideal because of the physiological adaptations that take place in a person’s body due to hypoxic (i.e. lack of oxygen) exposure. However, how altitude impacts running can be uncomfortable for the typical athlete. The changes that are experienced when transitioning from sea level to altitude and the overall effect on running will be discussed.
How Does Altitude Differ from Sea Level?
Altitude is typically expressed in feet in the United States (expressed in meters elsewhere) and is always relative to sea level, which is the level of the sea’s surface. To calculate this value, an average of various sea levels across the globe is acquired, with high and low tides taken into consideration. The highest altitude in the world is Mount Everest, which is 8,850 meters above sea level, or, 29,035 feet. For elite running purposes, most athletes train between 4,000 and 8,000 ft (1200 – 2400 m) above sea level.
Atmospherically, the air at altitude is thinner (less dense) than at sea level. This effect is due to reduced partial air pressure as altitude increases. Although there are the same number of oxygen molecules in the air at higher elevations, those molecules are spaced farther apart. Ultimately, this condition means that fewer oxygen molecules enter the body with each breath at altitude than at sea level.
Negative Effects of Altitude on Running
Runners experience a number of negative effects at altitude that can detract from their training. These negative effects include:
Decreased Oxygen Consumption
As mentioned above, there is less oxygen that can be consumed with each breath as altitude increases. Since oxygen provides fuel for muscles during endurance activity, decreased oxygen consumption hinders performance. In terms of VO2 max, which is the measure of the maximal amount of oxygen that can be consumed at exhaustive exercise performance, this value decreases as elevation increases.
For instance, in a study performed in Norway1, exercise scientists studied the effects of altitude on VO2 max relative to sea level. Participants in this study completed treadmill tests in simulated conditions at 300 m (984 ft), 800 m (2,624 ft), 1,300 m (4,265 ft), 1,800 m (5,905 ft), 2,300 m (7,646 ft), and 2,800 m (9,186 ft) above sea level through utilization of a hypobaric chamber. A linear decline in VO2 max was observed, with athletes experiencing 1.9% decrease in VO2 max for every 1,000 ft (~300 m) of elevation gain. In addition, for every 1,000 ft (~300 m) gain in altitude, time to exhausted decreased by 4.4%.
While decreased oxygen consumption will affect blood cells in imperceptible ways, a runner also experiences physical symptoms. For instance, at a similar effort that is expended at sea level, heart rate will be higher and breathing will feel more difficult. Combined, these two factors can make running feel physically more difficult. Anecdotally, athletes often liken the way that muscles and lungs feel while running at altitude to the feeling that is accompanied by anemia or low ferritin levels.
While there is no tried-and-true formula for determining just how much slower you will run at altitude, the fact of the matter is that it will be more difficult to sustain the same pace when you are running in the clouds than at sea level. With the previously stated decrease in VO2 max in mind, most runners can expect to experience a 30 – 45 second increase in pace per mile, regardless of effort.
Something that should be taken into consideration is that runners will be affected differently based on the aerobic demands of their workout. This trend can be clearly seen in the altitude conversion chart distributed by the National Collegiate Athletic Association, which is used for determining entry into national collegiate track and field meets.
For instance, when competing at ~7,000 ft (2130 m), male 10k runners are expected to run 97 seconds slower than their sea level counterparts. In the 800 m run, the difference is 1.27 seconds. For the 800 m runner, this conversion suggests the athlete is slowed 1.1%, while for the 10k runner the altitude slows the athlete by 5.6%.
Indeed, as an exercise becomes more anaerobic (without oxygen), altitude can actually lead to performance enhancement. One study2 suggests that an altitude of 1000 m (3280 ft) can improve 100 m sprint times by 0.19 seconds for men and 0.21 seconds for women.
Increased Risk of Dehydration
Training at altitude increases dehydration risk for a myriad of reasons. For one, the decreased oxygenation that athletes experience due to lower partial pressures in the air result in hyperventilation, which enhances oxygen utilization. Therefore, hyperventilation causes more evaporation loss from the lungs during exhalation and speeds up dehydration. Further, the lower air pressure also causes increased evaporation of moisture from the skin. Since many regions at altitude also have low humidity, the dry air at altitude can be particularly dehydrating.
Another factor at altitude is hypovolemia3, in which the body temporarily decreases blood / plasma volume. Often, people experience more frequent urination at altitude as a result of hypovolemia, which can lead to loss of hydration. However, hypovolemia also contributes to sodium loss which has similar symptoms as dehydration, but is altogether different.
Finally, training at high altitude can negatively impact running because of the development of altitude sickness4. There is no known link as to who is most susceptible to altitude sickness, but lack of adequate oxygen to muscles and tissues can result in symptoms such as nausea, loss of appetite, elevated heart rate, headache, difficulty sleeping, dizziness, and fatigue. Altitude sickness typically occurs at elevations above 6,000 ft.
Positive Effects of Running at Altitude
Of course, running at altitude isn’t all bad. Otherwise, elite runners would not flock to areas such as Boulder, CO and Flagstaff, AZ. There are numerous positive effects5 of running at altitude which unfortunately do not fully manifest until the runner returns to sea level. However, the very reason that running is difficult at altitude is also what causes the improvements when running at sea level.
Increased Red Blood Cell Volume
When training at high altitudes, the decreased amount of oxygen that can be consumed hinders the ability of red blood cells to carry oxygen to muscles and tissues. Since the body is adaptive, it creates more red blood cells in order to increase the amount of oxygen that can be supplied. This change is triggered by erythropoiten (EPO), which is a common performance enhancing drug that the body naturally produces in limited quantities.
In one study6, 12 male participants provided blood samples while training at different altitudes, and data such as red blood cell count, mean cell hemoglobin, mean corpuscular hemoglobin concentration, and mean cell volume were obtained. Blood tests were taken at sea level, 1830 m (6,000 ft), and 4000 m (13,123 ft) at 24, 48, and 72 hour increments.
While there was no change in mean cell hemoglobin count among the different altitudes within this period of time. However, increases in red blood cell volume at both 1830 m and 4000 m were significant, even after a short amount of time spent in thinner air.
Effect of Various Altitudes
How do varying altitudes affect runners? Although the hypoxic effect is most noticeable at 8,000 ft (2,438 m) or greater, exercise scientists have found that moderate adaptations can occur at altitudes as low as 2,000 ft (609 m). As stated previously, the amount of available oxygen in the air decreases with increasing elevation. The amount of oxygen in the air varies in the following manner:
• 2,000 ft: 7% less oxygen than at sea level
• 3,000 ft: 10% less oxygen than at sea level
• 4,000 ft: 13% less oxygen than at sea level
• 5,000 ft: 16% less oxygen than at sea level
• 6,000 ft: 19% less oxygen than at sea level
• 7,000 ft: 22% less oxygen than at sea level
• 8,000 ft: 24% less oxygen than at sea level
• 9,000 ft: 27% less oxygen than at sea level
Adaptations that occur in response to altitude training can last 10 – 20 days8 after returning to sea level. For maximum adaptations, athletes should spend at least 3 weeks training at elevation.
Train High / Sleep Low versus Train Low / Sleep High versus Train High / Live High
There have been many schools of thought as to whether it is most beneficial to train at high altitudes while sleeping at lower altitudes, training at low altitudes while sleeping at higher altitudes, or both training and sleeping at high altitudes. A significant body of research9 has suggested that constant exposure to high altitudes can lead to decreased VO2max, even after returning to sea level. The present school of thought is that training low10, where exercise intensity can be maximized, while living high and reaping the benefits of oxygen deprivation is optimal for competitive performance.
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2. Linthorne, Nicholas P. “Improvement in 100-m Sprint Performance at an Altitude of 2250 m.” MDPI. Multidisciplinary Digital Publishing Institute, 12 May 2016. Web. 01 July 2017. Link
3. Goldfarb-Rumyantzev AS, Alper SL. Short-term responses of the kidney to high altitude in mountain climbers. Nephrology Dialysis Transplantation. 2014;29(3):497-506. doi:10.1093/ndt/gft051. Link
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5. Saunders PU, Pyne DB, Gore CJ. Endurance training at altitude. High Alt Med Biol. 2009;10(2):135-48. Link
6. Hematy Y, Setorki M, Razavi A, Doudi M. Effect of altitude on some blood factors and its stability after leaving the altitude. Pak J Biol Sci. 2014;17(9):1052-7. Hematy Y, Setorki M, Razavi A, Doudi M. Effect of altitude on some blood factors and its stability after leaving the altitude. Pak J Biol Sci. 2014;17(9):1052-7. Link
8. Bailey DM, Davies B. Physiological implications of altitude training for endurance performance at sea level: a review. British Journal of Sports Medicine. 1997;31(3):183-190. Link
9. Adams WC, Bernauer EM, Dill DB, Bomar JB. Effects of equivalent sea-level and altitude training on VO2max and running performance. J Appl Physiol. 1975;39(2):262-6. Link
10. Wehrlin JP, Marti B. Live high‐train low associated with increased haemoglobin mass as preparation for the 2003 World Championships in two native European world class runners. British Journal of Sports Medicine. 2006;40(2):e3. doi:10.1136/bjsm.2005.019729. Link