Altitude Physiology: Your Body At Altitude You have probably heard of the idea that high altitudes make exercise performance more difficult. You may have seen high-altitude
climbers using oxygen tanks. You may have even heard of athletes living or training at altitude for periods of time in order to adapt. At the end of this article, you will understand what makes high altitudes so challenging, and how the human body adapts to this environment. Altitude Basics The primary difference between sea level and high-altitude (e.g. Mount Everest) is atmospheric pressure. Sea Level: Pressure = 760 mmHg Mt Everest: Pressure = 253 mmHg A common misconception is that high-altitude air contains a lower percentage of oxygen. This is untrue. Air at sea level contains the same relative amount of oxygen as air on Everest, ~ 21%. The difference is that the atmospheric pressure is roughly 1/3 that of sea level, meaning that you are getting just 1/3 the amount of oxygen due to the low pressure condition. I like to think of this as the oxygen being "spread out" more in the air, and therefore you are getting less absolute oxygen per breath taken.
Atmospheric pressure is also
impacted by weather, and thus is susceptible to change with the climate. The colder it is, the lower atmospheric pressure plunges, and thus winter climbs push further beyond the human physiological limit. When it is warm, and as the climate warms, Everest is actually easier, and
the summit may feel lower as a result (although long term climatic projections predict a decline in atmospheric oxygen levels, but this is on the order of hundreds and thousands of years). Fascinatingly, Everest
seems to be right at the cusp of the human physiological limit for climbs without oxygen; a funny coincidence of geographic-biologic synergy, or intentional design (you choose). The Body So, that's all well and good, but what about the body? How do we deal with it, and how do adaptations occur? Firstly, as is pretty intuitive, when we inhale less oxygen, we end up with lower levels of oxygen in the blood (hypoxia), increased heart and respiratory
rate, and elevated levels of carbon dioxide in the blood (hypercapnia). As a temporary state, this is tolerable, but as we push through this state, we will begin to see signs of failure, e.g. Acute Mountain Sickness (AMS), High Altitude Pulmonary Edema (HAPE), High Altitude Cerebral Edema (HACE). To get an understanding of some of the
responses & adaptations, here is an overview of the key differences in physiology between an average person acclimatising to altitude versus those who have lived their long term (Table 1).
Figure 3: Time course of acclimatisation at 4300m, Muza, S. R., Beidleman, B. A., & Fulco, C. S. (2010). Altitude preexposure recommendations for inducing acclimatization.
High altitude medicine & biology, 11(2), 87–92. https://doi.org/10.1089/ham.2010.1006 This is why, when people climb high peaks, they will often climb up during the day, sleep a little lower, and then repeat that process. They will also spend an extended period of time at camps (e.g. Everest Base Camp), allowing those adaptations to set. Conclusion High-altitude presents a novel challenge to the
human body, impacting all of your physiology. The lungs, heart, blood, kidneys, and more, are all involved in this process. Such responses to altitude may also be of benefit to elite endurance athletes, as they can avail of the increased oxygen-carrying capacity when they return to sea level (temporarily). For more on that, take a look at this paper. There is so much more to the altitude discussion, and if you happen to have any questions, just respond to this email and I will
be happy to answer them.
|
|
Dr Gary McGowan, MB BCh BAO, BSc |
This Week's Triage Content
YouTube: We published two new videos this week. Make sure you are subscribed to keep up, as 2023 will feature a heavy focus on YouTube videos (longer form vs instagram etc.) for us at Triage.
Grow Your Back With The Prone Row (Seal Row)
How to Create Diet Habits That Stick | Nutritionist Explains
Instagram: As always, we posted plenty of new content on Instagram this week, all of which you can find listed below for ease of
access.
Podcast: HOW TO TRAIN - Endurance | Triage Thoughts Ep. 270
In this episode of the podcast, we discuss how to train for endurance. Naturally, this is a very broad category of training, encompassing many different sports (such as marathon running), and we obviously can't cover every single nuance. However, by the end of the podcast, you should have a pretty solid idea
of what to focus on and a much better understanding of how to train for endurance. |
|
|
