Q&A: Dr. Anne Friedlander on High Altitude Exposure and Training

Recently, we sat down with Dr. Anne Friedlander, Stanford Exercise Physiology professor and Apeiron Life advisor, and Fred Harman, an Apeiron Life member and avid mountaineer, to discuss high altitude physiology and performance.

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Q: What are the age-related risks of going to extreme altitudes?

Dr. Friedlander: Aging can increase risk due to stress on systems like oxygen transport and heart rate. That said, older individuals aren’t necessarily more prone to altitude sickness (AMS). Some theories even suggest age-related brain shrinkage might reduce the risk for AMS due to less cranial pressure.

However, you tend to take fewer risks and know your body better as you get older. Adults often self-regulate, knowing their limits.

Q: Is it true Everest has a 20x higher fatality rate for climbers over 60?

Dr. Friedlander: I'm skeptical without seeing the data. Factors like extreme fatigue, inability to recover, or cardiac events could play a role. As we age, we become more susceptible to various challenges, altitude likely being one of them, particularly in terms of muscle function, temperature regulation, and similar factors.

Also, Everest's fame likely attracts less-fit or un-prepared climbers pursuing bucket-list goals, which may skew the stats.

Q: I used supplemental Oxygen during rest on Everest. Was that wise?

Dr. Friedlander: Absolutely. Smartest thing you did in that moment was to take that Oxygen. After intense elevated exertion, your heart rate increases, and blood flows more quickly, meaning Oxygen has less time to get into the blood, leading to Oxygen levels dropping even more. That drop can trigger altitude sickness and dangerous symptoms like breathlessness and exhaustion. Supplemental Oxygen helps stabilize the system.

Q: Thoughts on Diamox (the diuretic medication)?

Dr. Friedlander: Diamox has a couple of effects. As you acclimatize to higher altitudes, you lose plasma volume because your body is concentrating red blood cells to carry more Oxygen. You also release EPO, which gradually increases red blood cell production. Diamox, being a diuretic, speeds up that concentration process. However, one of its main functions is that it's a carbonic anhydrase inhibitor, which changes how CO2 is processed in the blood. This leads to slightly higher CO2 levels, stimulating you to breathe more.

When you're suffering with Cheyne-Stokes breathing, that cycle of over-breathing and then not breathing, you end up blowing off too much CO2, which can make you feel like you're suffocating. Diamox helps by keeping CO2 levels up, so your breathing stays more consistent and your oxygen levels stay higher.

Q: Can you take a lower dose of Diamox to avoid side effects?

Dr. Friedlander: Side effects like tingling or taste changes are common but hard to separate from general altitude symptoms. Some studies suggest that Diamox can have a slight negative performance effect. However, overall, the side effects are pretty benign, so following your physician's advice is best.

Q: I've been working with the Apeiron Life team on heart rate and strength training. One technique I focused on was to use my full posterior chain, both arms and legs, to propel myself upward. Could engaging my whole body like that have helped stabilize my heart rate?

Dr. Friedlander: Compared to the guides who likely hyper-focus all their strength into their legs, your technique is likely best for your body.

In terms of the heart rate, it's not uncommon that when you're at high altitude for long periods, the body adapts to get more Oxygen into the bloodstream (e.g., heart rate, ventilation, change in bicarb, etc.) As that happens, one of the changes that occurs is your plasma volume declines, and so your stroke volume (the amount of blood your heart pumps per beat) goes down. Your heart rate at altitude has a protective mechanism that downregulates max heart rate over time with chronic altitude exposure. The theory is that the body is protecting the heart tissue from working too hard at low oxygen levels.

So, over time, your submaximal workload may go up, but your VO2 max might not change much. These are offsetting adaptations.

Q. At the extreme altitudes, I noticed people's appetites were gone, and they took almost zero calories on some days, which led to serious muscle loss. Why does the body lose muscle at altitude instead of burning fat?

Dr. Friedlander: Fats burn in the fire of carbohydrates; without carbohydrates, we can't access and process the fat held within our bodies. In order to keep the TCA cycle delivering energy, the body requires carbohydrates to process the fat. If you're restricting your carbohydrates, the body has to turn to protein stores (e.g., muscle). The body can use the Amino Acids from that protein as a substitute for carbohydrates, but it can't process fat alone.

At rest, you're using 5-10% of your protein calories to keep yourself alive, but if you don't have the carbohydrates around, you break down muscle! You eat away at the lean tissue without the right fuel sources, especially during times of high stress, like extreme altitudes.

One study we conducted saw a beneficial adaptive response to appetite suppression at altitude. The theory was that if you're carrying less body mass, do you need less Oxygen, and if your muscles are shrinking but your vessels aren't changing, is there a shorter diffusion distance for the Oxygen to have to travel? What we found was that for any exercise involving moving body weight (e.g., hiking), performance increased, but for any strength-based requirement, performance decreased.

Therefore, the adaptive loss of appetite at these extreme altitudes may have a physiological reasoning.

Q: Are oxygen-enriched hotel rooms helpful, or is it just marketing and may inhibit acclimatization?

Dr. Friedlander: If you're going up for a vacation to see the views, sure you'll probably sleep more comfortably in the high-oxygenated rooms.

But if you're going to do any high-altitude exercise (e.g., skiing), you may be doing your body a disservice as you're missing the acclimatization that occurs overnight. Many adaptations occur in these types of environments, and artificially skipping them may lead to a loss of beneficial outcomes.

One study we did provided supplemental antioxidants to review oxidative stress at altitude. We found that these free radicals (reactive oxygen species) were the signaling molecules, so preventing their occurrence meant we saw a muted adaptogen response.

As with resistance training, if given a high-dose Vitamin C, you will mute your adaptive response. Therefore, I wouldn't recommend the high-oxygenated rooms for adaptive health purposes.

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My final thought for you is a small warning regarding high-altitude activities. There is some data to suggest that individuals who are repeatedly exposed to high elevations develop brain lesions that form from the chronic low-oxygen state.

So far, there has not been a direct link between that outcome and cognitive health decline or issues like dementia. However, brain changes can occur, so I wouldn't recommend repeatedly spending any prolonged time above 18,000 feet.

However, mountaineering is a fantastic endeavor in many other ways, from mental health to fitness, so keep climbing (just at lower altitudes).