If you are interested in altitude training, Randall Wilber’s book “Altitude Training and Athletic Performance” is a fantastic read. I apologize for the lack of posts recently, but I’m recovering from arthroscopic hip surgery last week and am not up for doing a whole lot of sitting (in fact, I’m typing this out standing at my desk, balanced on my good leg!).
To compensate, I’ll post the fairly extensive notes I took while reading Wilber’s book a few years ago. Since these were personal notes, I’ll also have to apologize for the many instances of typos and misspellings too! Anyways, hopefully you’ll find this helpful and interesting if you ever plan on being at altitude for training or non-training purposes. Enjoy! [Article revised in 2022 with a few comments like this in brackets - JD]
Potential physiological benefits of altitude training for runners
When a runner is exposed to altitude, the body makes several rapid adjustments:
Cardiac output and stroke volume drops. This is true during both in submaximal and maximal exercise.
Ventilation increases, meaning the total flow of air in and out of the lungs goes up.
This increase in ventilation, coupled with hormonal changes causing an increase in urination, gives rise to a great increase in the body’s demand for water.
Because the body needs more water, fluid intake at altitude should be up to 4-5 liters per day. This is especially true during the acclimatization period.
Lactate buffering is impaired during adaptation to altitude because the increase in CO2 exhalation disrupts the equilibrium of the bicarbonate buffering system, allowing H+ to accumulate faster.
In men, carbohydrate utilization increases; that is, a larger proportion of the athlete’s daily energy comes from carbohydrates. Women maintain a similar level of carbohydrate and fat utilization vs. sea level. Both men and women will likely need to increase their caloric intake, but men in particular must consume extra carbohydrates. High-glycemic food ought to be consumed immediately after exercise at altitude.
At altitude, your body requires more iron to produce red blood cells. Without an iron supplement, the ferritin levels of lowland athletes training at altitude often drops significantly. Furthermore, athletes who are iron-deficient upon ascent (defined in one study as men with <30 ng/ml ferritin and women with <20 ng/ml) respond very poorly to altitude. Therefore, iron supplements are a necessity. One study prescribes 5-45 ml/day of a 9mg/ml liquid iron solution, depending on ferritin levels [Note: as of 2022 I no longer recommend liquid iron supplements - JD].
Altitude exposure increases levels of the stress hormone cortisol. The increase in oxygen demand, coupled with increased training at altitude, results in an increase of cortisol, a stress hormone. Cortisol can impair training and depress the immune system, making athletes more susceptible to illness. It can also cause muscle catabolysis, where the body “eats” its own skeletal muscles. This muscle catabolysis may be able to be counteracted by consuming protein after exercise and before bed.
Oxidative stress increases at altitude, possibly because of the increased oxygen consumption, increased UV exposure, and free radical production. Oxidative damage can result in fatigue, DOMS, and injury. Wilber suggests supplementation with 400mg of vitamin E per day to counteract oxidative damage. Wilber also mentions sunblock, sunglasses, vitamin A, and vitamin C. Other (and more natural) antioxidant sources, such as tea, pomegranate juice, blueberries, and grape juice, will likely also go a long ways towards protecting the body [Note: as of 2022 I discourage runners from taking supplemental antioxidants such as vitamin E and C because oxidative stress is part of the simulus on the body to adapt to training -JD].
Under proper diet and hydration, body composition should not drastically change. Body composition meaning weight and also body fat / lean body mass balance.
Altitude training and performance in runners
Results from many years of studies [As of the book's publication date which was 2003; more evidence in favor of altitude training has accumulated since then - JD] are inconclusive on whether altitude training improves sea-level performance in trained athletes. Problems result from poor methodology, lack of a control group at sea level, different training protocols, and small study numbers.
Live-high, train-low for endurance athletes? In a retrospective investigation into “responders” and “non-responders,” over 80% of “responders” (people who improved after altitude training) were in the “Live High, Train Low” training group. The rest were in the traditional “Live High, Train High” group. [Note: as of 2022 I am very skeptical of studies from the last 30-40 years on "responders" vs. "non-responders" for methodological reasons outlined in this scientific paper - JD]
Wilber hypothesizes that the ability to do maximal and near-maximal training at near sea level allows athletes to retain the training intensity of sea-level groups but reap the physiological benefits of altitude [Other physiologists who currently work on altitude training as of 2022 seem to have coalesced around this belief - JD].
Among the studies supporting the benefits of the live-high-train-low approach, the greatest benefits seem to be from groups training and living between 7,000 and 10,000 feet.
At the very least, training at up to 10,000' elevation won't make you slower. Of studies not supporting the benefits of the live-high train-low approach, the only groups with statistically significant decreases in performance, VO2 max, and Hemoglobin levels lived and trained at over 13,000 feet.
Therefore, we can conclude that, at the very least, you will not get worse by training and living at altitude in any city in the United States. Up to 10,000 feet seems to be a safe altitude.
Recent well-designed studies by Levine and Stray-Gundersen suggest that 1) Live-high train-low is superior to sea-level training for periods of training on the order of one month and 2) Base training at altitude and faster training at low altitude (so-called “Hi-Hi-Lo” training) is equally good.
From argument, it seems obvious that the best choice for "DIY altitude training" would be HiHiLo training, because it would save on trips down from the mountains.
One recent study asserts that athletes can be divided into “responders” and “non-responders” based on their blood EPO levels (% of sea level baseline: responders had a blood EPO increase of ~156% after 30h and nonresponders increased only ~137% of SL base) and total red cell volume (ml/kg) (total red cell volume increased in responders significantly (~3.0 ml/kg) and remained unchanged in nonresponders). [See above note and related paper re: problems with binning people into "responders" and "nonresponders" - JD]
“After 14 days at altitude, EPO was still elevated in responders but was not significantly different from sea-level values in nonresponders” - Wilber [Note: Methods here might be example of the so-called "DINS error" -JD]
“In conclusion, after a 28-day altitude training camp, a significant improvement in 5,000-m run performance is, in part, dependent on 1) living at a high enough altitude to achieve a large acute increase in EPO, sufficient to increase the total red cell volume and VO2max, and 2) training at a low enough altitude to maintain interval training velocity and O2 flux near sea-level values.” - Wilber
Practical implementation of altitude training for runners
Most successful coaches and athletes recommend 7-10 days of acclimatization upon ascent to altitude before intense training begins.
Programs differ during the “stress” phase, but it lasts from 2 to 6 weeks. Before return to sea level for competition, a week or so of backed-off training is recommended to absorb the hard training. This may not be necessary if hard workouts are done at low altitude (i.e. if doing live-high, train-low).