Attitude With Altitude

Let’s talk about altitude! I have spent a lot of time researching and discussing this topic with other coaches and physiologists, and have come to the conclusion that it’s incredibly complicated and varies tremendously amongst athletes. Additionally, new research shows that an athlete’s response to altitude and altitude training also varies stimulus to stimulus... 

First, let’s go over the things that we do know before tackling the somewhat ‘abstract’ science of altitude physiology. The largest consideration that comes to mind with performance at altitude is the lack of oxygen in the surrounding environment. Our surrounding ‘atmosphere’ consists of nitrogen, oxygen, and carbon dioxide. The ‘partial pressure’ of each gas is the same at sea level as it is at altitude (i.e. oxygen makes up the same percentage of the atmosphere in San Diego as it does on top of Mt. Everest). Interestingly, this is the reason that some believe altitude tents aren’t all that helpful when trying to train for an event at altitude. Tents remove oxygen from the surrounding atmosphere while keeping the atmospheric pressure the same. Therefore, nitrogen and carbon dioxide now make a higher percentage in the tent than they do in San Diego possibly inducing less adaptations that would be beneficial at altitude. 

I would also like to note that ‘altitude masks’ are essentially snake oil. Masks that make it harder to breathe stress the mechanisms of breathing, but don’t induce adaptations that occur when less oxygen reaches the bloodstream (we’re all kind of doing this when running in masks in the world of COVID). 

So...what happens when we’re exposed to an environment that has a lower partial pressure of oxygen (less oxygen). Well, the most obvious change is to our aerobic energy systems. If you can run a 9 min/mile at a HR of 150 bpm at sea level, this same pace will occur at an elevated HR at altitude since the heart works harder to pump less oxygen-rich blood to our working muscles. Additionally, the stroke volume of the heart decreases as we’ll discuss below.

One immediate adaptation that occurs when we go from low to high altitudes is a quick drop in blood volume by ditching blood plasma. The term ‘hematocrit’ is used to describe the percentage of red blood cells (RBC) to total blood volume. RBC carry oxygen molecules and this is incredibly important to aerobic function during exercise. So our body gets rid of other ‘blood stuff’ to increase hematocrit and try to get the oxygen to our cells when less of it is available.

Interestingly, one method that has been proposed to counteract this loss in blood volume that occurs when you’re first exposed to altitude is to spend time in the sauna or other hot environments as you prepare. Saunas are known to increase blood volume and in the process, RBC production increases to maintain hematocrit levels (remember, this is just a percentage of RBC to total blood volume). Therefore, when you go to altitude and blood volume decreases, you should have an even higher relative hematocrit and be even better at oxygen delivery. 

The sauna protocol for altitude preparation is something that seems ‘off’ to me. I understand that increased RBC increases oxygen delivery (the mechanism of blood doping). However, trying to time seems difficult and I do see some downsides if the timing is off. Let’s say that you hop in the sauna 2 weeks before an event. Blood plasma increases pretty quickly, so your blood volume will increase pretty quickly. RBC production doesn’t occur as fast (as noticed during altitude performance studies) and it’s very possible you will be going to your race with a lot of blood, but no more RBCs than before. Now, your body has to ditch ‘more volume’ and the time you spent in the sauna was a waste. Moreover, that time in the sauna was an additional stressor and could take away from your time spent training and recovering! Here’s an article of David’s that supports the use of sauna usage for altitude performance and a protocol that he suggests. I suppose I just don’t fully believe or understand it just yet! 

Another consideration for living and training at altitude is that you are more limited by blood delivery. As blood volume decreases at altitude to maintain a higher hematocrit value, your heart has to work more to move the same amount of blood. Your ‘stroke volume’ is decreased, and HR has to increase to compensate. Since oxygen delivery is diminished, your VO2 max decreases (your ability to utilize oxygen) and running occurs at a higher relative percentage of VO2 max and higher HR. Consider an athlete training for a marathon who lives at 9k’ elevation as compared to one living at sea level. If this athlete wants to run a 7:30 pace for an upcoming marathon and has to replicate this pace in training, it will be occurring at a higher percentage of VO2 max. While this may improve some aerobic developments, it may also be damaging some aerobic capacity as more energy has to be produced from anaerobic means…

The above is complicated, but a quick refresher. We run ‘easy’ to develop aerobically. Capillary density, mitochondria production, recruitment of slow twitch muscle fibers, etc… all occur when we’re logging those easy miles. If those easy miles are no longer ‘easy’ at the same pace, we may be underdeveloping those aerobic adaptations. Additionally, there’s a certain efficiency that we gain when running more volume at a target race pace. You recruit the ‘right’ muscle fibers and your body develops an efficiency at that slightly faster pace. 

This is the theory behind living high and training low. In this perfect ‘training world’, an athlete is able to boost RBC production by living at altitude, but reap the benefits of training at a lower altitude (i.e. faster turnover and pace for a given metabolic cost). Unfortunately, this is a very hard world to replicate. I remember when Ellie and I were in the van. Bishop and Mammoth, CA made a wonderful ‘live high train low’ environment as you could sleep at 9,000’ and drop to 4,000’ in a 30 minute drive. Granted, it was the middle of the winter, and the van wasn’t the best suited for winter conditions. 

Lastly, let’s talk about the metabolic repercussions of being at altitude. We have discussed it before, but the crossover point is the intensity of running (measured by percentage of VO2 max) that the body switches from fat metabolism to carbohydrate metabolism. This crossover point is usually defined as the heart rate that’s a certain percentage of VO2 max (usually around 65% depending on the athlete) where carbohydrate metabolism is preferred to fat metabolism. As VO2 max decreases, this occurs at a lower and lower pace. So… when you’re at altitude, you’ll likely need a higher intake of dietary carbohydrates during longer races. Additionally, fat oxidation for energy production comes at a higher cost of oxygen consumption.This may inhibit energy production used via this metabolic system when oxygen is a premium. 

There is a lot of information above and most of it is hard to implement in training in any real way. Most of us don’t have access to high altitude training (either in the form of a tent or the surrounding environment) and this can feel rather limiting when trying to be fully prepared on race day. The best approach is to become as fit as possible, make sure energy levels are high, and possibly increase the intake of B12 and iron in training before the event. We can dive into the reasoning behind this later, but iron allows increased oxygen transport in the blood, and B12 may assist in energy production from carbohydrate metabolism.