Sleep High, Train Low: How 6 months sleeping in an altitude tent impacted my running performance

By: Ruby Wyles

Early August, with a collegiate cross country season just around the corner, I had high hopes and ambitious goals. Eager to optimize my lifestyle to support my athletic performance, I took my university studies in exercise science home with me and set about answering my own research question: are altitude tents worth it, and can they actually have a noticeable effect on performance?

Test subject: me, researcher: myself, and data analyst: I. Me, myself and I followed the same basic study protocol: at least 8 hours in an altitude tent daily. I make light of that to illustrate that this is solely my personal experience, not a peer-reviewed article or double-blind controlled trial.

So, over the past couple months I have been trying something new: sleeping at altitude. Advocates claim that altitude tents allow you to benefit from the effects of altitude without leaving your sea-level home, making it more affordable and accessible than moving to the mountains! They claim that in just 3-4 weeks, spending 6-8 hours per day in the simulated altitude environment created by the generator can yield measurable results: get faster while you sleep!

Why altitude?

As exercise physiologists and researchers continue to explain, exposure to altitude can markedly improve athletic performance in endurance events like distance running and triathlon. At higher elevations, the amount of oxygen in the atmosphere decreases, so your body has to work harder to supply working muscles and vital organs with sufficient oxygen and nutrients. After an initial adjustment period of a few days to weeks, our bodies compensate for this lack of oxygen by increasing the secretion of the hormone EPO into the blood, resulting in the bone marrow producing more red blood cells, so that more of the oxygen in the air that we breathe into our lungs can be absorbed into the bloodstream. Our bodies benefit from increased capillarization in working muscles and vital organs, delivering more blood, hence more oxygen, to the tissues. In short, exposure to altitude makes us more efficient at extracting oxygen from the air into our blood and delivering oxygen to our tissues.

This physiological adaptation in response to altitude has big benefits to endurance performance at sea level: with more red blood cells, alongside the increased oxygen at sea level, you are able to absorb even more oxygen into the blood and then transport that to the working muscles than possible prior to altitude training. Oxygen is a limiting factor to aerobic activities; the best performers are able to work longer and harder aerobically, without accumulating lactate or oxygen debt, without fatiguing. Through both real and simulated altitude training, endurance athletes can legally raise their Vo2 max, boosting performance.

Tent set up

Leveling up my commitment to my biggest running goals, I placed an order for the MAG-20 Higher Peak Sleep System, everything I hoped to need to set up my own simulated altitude environment. I received a large, heavy box containing a generator and lots of tubing, and in a smaller box came the tent apparatus. Much to my benefit, simple yet detailed instructions accompanied the equipment, with real useful pictures and a large legible font.

Constructing the tent was a step-wise process of threading tent poles through canvas and pegs; the hardest part being finding a large enough space in my small apartment to pop up the tent. Once built, I placed my mattress and bedding inside, zipping up the canvas to create a closed environment. Using the tubes, I connected the generator to the air bag to the inside of the tent, then plugged in the generator and turned on the machine. Instructions carefully guide on setting the simulated elevation level for the tent, with the dials on the generator making it easy to adjust accordingly. The generator also allows for different pre-programmed modes, and a timer on top adds up the time spent at altitude, which I have found really helpful when recording how long I have been inside my tent.

On the other hand, a big disadvantage of the generator is the waste noise and heat that it produces when switched on. To get around this problem, I keep my generator outside my bedroom and thread the tubing under my closed bedroom door: a fan is a great tool to dispel the heat.

Early days

As per the advice provided by Higher Peak, adjusting from sleeping at sea level to the altitude environment created by this Sleep System is best done gradually. This first week I dialed up the ball meter to a 6 out of 10, which is meant to generate an altitude equivalent to XX feet above sea level.

As much as I wished for a different report, these seven days were rather difficult as I struggled to sleep because of the noise and heat emitted from the generator, alongside lingering warmth of Summer nights. I found myself taking some extreme measures, wearing an eye mask and earplugs, setting up multiple fans inside and outside my tent, and draping a cold towel around my neck as I laid in bed. My long term solution to this problem is keeping the generator outside my bedroom and threading the tubing under my closed bedroom door: a fan is a great tool to dispel the heat.

I mistakenly assumed that the biggest challenge would be aerobically as a direct result of a lower partial pressure of oxygen: in fact, I never noticed any additional strain on my respiratory system. The only negative effects I encountered this first week sleeping at altitude were as a result of greatly reduced sleep quality and quantity, rather than the actual altitude: my training and performance suffered as a consequence of this general fatigue. As I took more additional measures to minimize the disturbance of the generator, alongside sheer persistence and mounting fatigue, my sleep improved and I definitely began to get used to my new night-time routine.

Sleeping high, training low: putting theory into practice

The first 8 weeks I followed Higher Peak’s recommended protocol, before adjusting to better suit my needs. I also had the opportunity to take blood tests at different times in my self-experiment.

Weeks 1-4 constituted the acclimatization phase, whereby I progressed the altitude intensity from 5000ft week 1, to 7000ft week 2, then to 9000ft and 10,000ft week 4. Training intensity was maintained as altitude provided the added stimulus to my workload. Come week 3, I had my best race of the season when running at altitude in North Carolina. I believe that my body’s adaptations from sleeping at altitude prepared me to compete better at elevation, giving me the upper edge over my sea-level residing competitors.

Despite the added stress of sleeping at alitude, I didn’t notice any negative impact to my training or performance that could not be explained by a slight lack in overall sleep quantity.

Now adjusted to sleeping in my tent at 10,000ft, the next month was marked by a plateau in altitude. ***

As the Fall season wore on, my performances declined and mentally I struggled. Given my demanding schedule -balancing collegiate athletics, university studies and multiple part-time jobs- I decided to step down the simulated altitude from over 10,000ft to around 7,000ft: the elevation of the running hotbed of Flagstaff. Unsure about the cause of my declining performance, I worried that fatigue, decreased recovery and iron status could be limiting factors. Reducing the altitude was an attempt to address the first two, and fortunately a blood panel confirmed healthy iron levels. Despite these adjustments, the performance trend continued, leaving me to conclude positively that sleeping at altitude was not limiting my performance: that was still a mystery. 

For the last couple months, I have continued to spend 10-12 hours in my altitude tent at 7,000ft. Without the pressure of competing regularly, my training has improved and I look forward to racing in the New Year.

Sleeping high, training low: unpacking my bloodwork

In an attempt to remove some subjectivity, alongside optimizing my health, it was important for me to be able to track my blood biomarkers like iron and hematocrit: key determinants of the blood’s oxygen carrying capacity.

Then came the twist: week 3 in my tent, the same week as my best race of the season, blood tests revealed extremely low iron levels. A dip in iron status is a common consequence of altitude exposure, however, this finding is at odds with my performance! With such low iron levels, one would expect markedly impaired performance; I guess science can’t tell us everything!

 Most recently, post cross country season and 4 months sleeping in an altitude tent, off the back of some very disappointing performances, I had another blood test. Much to my suprise, my iron status had improved back to the lower-normal range, demonstrating how well the body’s physiology adapts to the stress of altitude.

Going forward

As track season comes around, spending time in my altitude tent is a habit I will continue. Starting at the baseline of 7,000ft that I’ve become accustomed to, I plan to step up the altitude more gradually by about 1,000ft every 2-3 weeks. As key races come around, I will periodize my altitude so that my recovery is not compromised and fatigue is minimized.

While I do not have conclusive evidence that I am performing better directly because of sleeping at altitude, I firmly believe that it is a marginal gain worth maintaining. Physiologically, my red blood cells have adjusted to sleeping at altitude, and psychologically, I feel more prepared going into races with altitude adaptations as tools in my toolbox. For me, my altitude tent is here to stay!