Two-day residence at 2500 m to 4300 m does not affect subsequent exercise performance at 4300 m
Link to research paper
What role does altitude play in training and racing?
The impacts of altitude on athletic performance have always fascinated me. Maybe this is because I have never been able to perform well at altitude… or maybe it is simply driven by my curiosity to understand a topic that carries with it much misconception in the endurance community. What is the real impact of “altitude training”? How long does one need to spend at altitude to garner beneficial physiological changes? Can training at altitude really improve your performance? What should one expect when choosing to race at altitude? These are the questions I will help you answer today, and questions that the paper I have chosen to share this month will help me answer for you as well.
I will begin by stating that the most common misconception behind altitude and performance is the idea that one can train at altitude for a few days and receive a benefit. This is not the case and, actually, training at altitude acutely (for a short period of time) negatively impacts your performance. Why? At altitude (the negative effects can be seen in lower elevations beginning at a few thousand feet, but really kick in at altitudes of above 5,000 feet), there is a lower partial pressure of oxygen. This does not mean there is lessoxygen as, in fact, the percentage of oxygen molecules in the air remains the same as it does at sea level at ~21%. A lower partial pressure of oxygen means that there is less pressure in the air around you pushing oxygen into your system when you breathe. This ultimately means less oxygen gets into your system, causing reduced performance capacity. In order to overcome these detrimental effects of altitude on performance, you need to be exposed to altitude chronically (for a long period of time), which in the case of altitude acclimatization only begins to take place after days of exposure. It can take upwards of 3-6 weeks to fully adjust and adapt to altitude, but only through constant exposure on a regular basis, for the majority of the day, and for days and weeks at a time… which basically means you need to live at altitude for 3-6 weeks to fully acclimatize and see the benefits. (Yes, unfortunately, this means that all of those “altitude training” masks and single days spent training at altitude don’t really carry with them the benefits you were hoping for…) What are these benefits of altitude adaptation? Due to the lower partial pressure of oxygen in the air surrounding you, your body begins to produce more red blood cells. More red blood cells give you a greater oxygen carrying capacity. Performance at altitude will never quite be the same as it is at sea level, even when fully adapted to altitude, but the increase in red blood cell volume will carry with it a big performance benefit when racing back at lower elevations or at sea level. It is this reason why so many professional endurance athletes will perform 3-6-week training camps at elevation or, just simply live at elevation!
I know what you’re thinking… this is all kind of depressing news because many of us don’t have the option to live at altitudes above 5,000 feet and many of us also don’t have the resources, time, or money to live at altitude for extended, 3-6-week training camps to glean the benefits of altitude exposure. I’m here to tell you that there aren’t really any other ways of gaining the benefits of altitude adaptation outside of taking illegal drugs (EPO is a big one). Yes, there are altitude tents and altitude training masks, but these don’t carry with them the research to truly back up their effects.
Despite the unfortunate truth that many of us won’t be able to attain the benefits of living at altitude for extended periods of time (if you live at elevation… I’m kind of jealous…); however, many of us still like to choose races at altitude. Aside from fully acclimatizing to altitude, athletes racing at altitude need to be aware of the impact that altitude will have on their performance and understand potential strategies to mitigate these effects. Acclimatization to altitude begins setting in within days, and this acclimatization can lessen some of the effects of altitude on performance, but how many days does one need to be exposed to altitude for these effects to set in? How should one approach their next race that takes place at altitude? The study I will share with you today helps us answer these questions.
What did the researchers study?
The methods of this study were a bit complex, so I will simplify them here for you. Essentially, researchers enrolled 66 men and women who lived at sea level and randomly assigned them to one of eight different groups for TWOdays:
1. Sedentary group at 2500 meters
2. Active group at 2500 meters
3. Sedentary group at 3000 meters
4. Active group at 3000 meters
5. Sedentary group at 3500 meters
6. Active group at 3500 meters
7. Sedentary group at 4300 meters
8. Active group at 4300 meters
*The sedentary group did not perform any exercise while living at altitude for the two days of the experiment, while the active group went on an ~90-minute hike each day during the experiment.
All 66 study participants performed a 5-mile, self-paced time trial at sea level before the experiment and again immediately after the two-day experiment at 4300 meters. The researchers aimed to see what the effects of acclimatizing to various altitudes and with different activity profiles were on subsequent exercise performance at 4300 meters. Researchers used validated prediction equations to predict the decrease in running performance times within the 5-mile time trial if one were to go immediately up to 4300 meters, and used this predicted performance time to compare actual performances of the study participants when they did the 5-mile time trial after acclimatizing at various altitudes for two-days. Note: For those of us here in the US that go by feet and not meters, 1 meter = ~3.3 feet, which means that 4300 meters = ~14,100 feet.
What are the major findings?
Essentially, the researchers found that two days of acclimatizing to altitude at various altitudes (2500 meters, 3000 meters, 3500 meters, and 4300 meters) did not attenuate any of the negative effects of altitude on subsequent 5-mile time trial performance. The 5-mile time trial times all matched up to what was predicted if one were to immediately go from sea level to 4300 meters and perform a 5-mile time trial.
What do these findings mean to YOU as an endurance athlete or coach?
Basically, what this means is that two days of acclimatizing to altitude (regardless of whether one was active or sedentary for two days at 2500, 3000, 3500, or 4300 meters), there were NO BENEFITS TO PERFORMANCE! The authors went on to say that they have conducted research, and others have as well, that has shown that acclimatizing to altitude for six days has been shown to improve performance at altitude, suggesting that longer periods than two days of acclimatizing is needed if looking to mitigate the effects of altitude on performance.
So… what does this mean for you as an endurance athlete or coach? I’ll summarize in a few bullet points:
Training at altitude for a day or two will NOT give you a performance benefit, it will only hurt your performance within training sessions conducted at altitude and will take you longer to recover from them. When going up to altitude to train, try avoiding “key” sessions that require intense efforts or quality efforts as your performance in these sessions, and the adaptations that will result from these sessions, will suffer. Keep training sessions at altitude, if you are there for only a few days, relatively light or aerobic.
Fully adapting to altitude and gaining the long-term benefits (increased red blood cell volume) takes months, and there is very little you can do to get these benefits outside of spending this much time living up at altitude. Don’t fall prey to gimmicks and products that try to advertise themselves as “altitude” simulating as they likely don’t have much research to back them up and, well as you already know, the only long-term benefit you get from altitude is from actually LIVING at altitude for weeks and months at a time.
If you are planning on racing at altitude, know that your performance WILL suffer when compared to racing at sea level. A good rule of thumb would be to plan for a 1-2% reduction in capacity for every 1,000 feet of elevation gain. See the following article from TrainingPeaks for more details on this: https://www.trainingpeaks.com/blog/the-effect-of-racing-at-altitude/. For example, if I am a triathlete and I want to hold 250 watts in a bike leg of a race, but I am planning on going up and racing at 5,000 feet and I normally live at sea level, I should expect to hold ~225-238 watts (~5-10% less than 250 watts) in the race at 5,000 feet to account for the negative effects of elevation on performance. This similar philosophy could be applied to running paces as well.
If you are planning on acclimatizing to altitude before you race in it, try giving yourself at least 5-6 days to begin to see a benefit as research tends to point towards six days or so when acclimatizing. There will still be a negative effect of altitude on your performance, but it may be slightly less than if you were NOT to acclimatize. Again, see the TrainingPeaks article above as they include a table with the expected % reductions in capacity based on elevation and whether or not one is acclimatized or not to the altitude they are training/racing in.
I have not mentioned this yet, but regardless of whether you are training or racing at altitude, keep in mind that you need to drink more fluids at higher elevations than you would at sea level. This is the case because higher elevations tend to be drier (dehydrates you faster) and because the initial acute compensation when exercising at altitude is an increased breathing rate (for more oxygen intake), and this will lead to quicker dehydration as well because we lose tiny amounts of water with each exhale. So, be sure to drink more at altitude than you normally would at lower elevations!
There you have it. A little insight into the intricacies of altitude, including adapting to altitude as well as realistic expectations when training and racing at altitude. Of course, like most other topics within the realm of endurance sport science, it is constantly evolving. More is sure to be learned about altitude, including acclimatizing to altitude, as researchers continue to study th topic. For now, take the lessons learned and apply them to your training or coaching when appropriate.
Happy training and racing!
-Ryan Eckert, MS, CSC