AltoLab ULTRA Portable Altitude Simulator Kit


Basic summary: AltoLab combines a set of breathing apparatuses with completely developed training programs to function as a high altitude simulator for Intermittent Hypoxic Training (IHT), a method that has been shown to improve physiologic indicators and exercise performance for a wide range of athletes. The ULTRA kit comes with all the equipment you need to start an IHT program, and prolonged use requires purchase of additional hypoxic silos. We tested the device for eight weeks in preparation for the Hardrock 100 Endurance Run with generally beneficial results.

MSRP: $629 for ULTRA Kit. Additional hypoxic silos are $29 each or $108 for 6.


  • 6 Hypoxic Silos (CO2 scrubbers)
  • 6 AltoMixers
  • 2 breathing filters
  • Breathing kit with mouthpiece, swivel tube, and connectors
  • Nose clip
  • Finger pulse oximeter with color display, lanyard, instructions and batteries
  • Training manual with multiple plans to choose from based on goals
  • Digital timer
  • Flash-drive containing latest scientific information and videos on IHT
  • Canvas zipper bag
  • Travel canvas carry-on bag

Deep dive:

Not every ultrarunner can live in the mountains, but it’s almost impossible for most of us to resist the allure of high altitude endurance events. The best way to prepare your body for a high elevation event is to arrive in the high country at least two weeks in advance and gradually acclimate to the thin air – but from a logistic or economic standpoint, that’s not always a feasible option.

So if you want to mimic the physiological conditions of living at high altitude, your choices are to go the low-budget route of Darth Vader-style simulator masks – which have been widely proven to be ineffective – or spend several thousand dollars on an altitude tent that transforms your bed or an entire room into a low-oxygen environment. Fortunately, there is an in-between option that is relatively affordable and has been scientifically proven to create physiological changes that are similar to high-altitude adaptation. The concept is Intermittent Hypoxic Training (IHT), and AltoLab is one of the forerunners in developing products in this category.

A number of professional athletes from the track and field community, and endurance athletes including ultrarunners, are gradually incorporating IHT into their regular training regimens. Used correctly and consistently, IHT training stimulates your body into producing more red blood cells, thereby increasing its oxygen-carrying capacity. It can also impact muscle physiology with increased myoglobin percentage and mitochondrial volume, effectively making your muscles more aerobically efficient, better at fat burning, and quicker to clear lactic acid out of your system. Studies have shown that IHT can produce a 2-3% increase in overall exercise performance, and from a regulatory standpoint, it’s perfectly legal: the World Anti-Doping Association (WADA) has ruled that altitude simulators are permissible for athletes to use in preparation for athletic competition.

But does it work for non-sponsored, non-elite athletes? This summer, we had the perfect test scenario: one of our editors (that would be me), who lives at sea level, was a lucky winner in the Hardrock 100 lottery. Spending two weeks in the San Juan Mountains prior to race day wasn’t an option, and sealing the bed in a tent for three months could have caused significant marital discord… so IHT seemed like a great approach to hopefully offset the physiologic shock that would happen when I showed up in Silverton the day before the race. I got my hands on the AltoLab ULTRA kit a few months beforehand, and followed one of AltoLab’s prescribed training regimens for eight weeks before flying out to Colorado.

You don’t need to have any coaching knowledge to figure out what to do with the device: every AltoLab kit comes with a set of eight training schedules to choose from depending on your goals and time schedule. My training plan called for 15 straight days of use, followed by two weeks of non-use, and then two six-day “top-off” cycles in the final weeks leading up to the event. All of the specific parameters of each training session are spelled out for you; all you have to do is follow the instructions and dedicate about an hour per day to the routine.

Here’s how it works: You sit in a chair and breathe through a mouthpiece while wearing a nose clip. The mouthpiece is attached to a flexible plastic tube that is connected to something called a hypoxic silo, which is where the “magic” happens. The green hypoxic silo captures your exhaled air, which typically contains 8-12% oxygen, as compared to about 20% oxygen in the regular (sea level) air you inhale. The silo absorbs and removes the expelled CO2 that you breathe out, and the remaining 10% oxygen air you expelled then mixes with each inhalation of regular room air to gradually decrease the net oxygen percentage of the air you are breathing in.

Attached to the other side of the hypoxic silo is a number of black altomixers, which are stuffed with soft perforated foam, which provides the environment for lower percentage oxygen to mix with the room air being inhaled. The altomixers can be stacked upon each other, and increasing the number of altomixers creates a larger quantity of low percentage air to mix with regular air, which simulates higher altitudes by gradually decreasing the oxygen concentration of the air you breathe. While you’re breathing, you also wear a pulse oximeter on your finger which indicates the oxygen saturation (SaO2) of your blood, if the percentage decreases too far, you’re supposed to “cheat” a little by opening your lips briefly to inhale a bit more room air and stay within a target SaO2 range. You keep the mouthpiece and nose clip in place for 6 minutes, then take it off for 4 minutes, and repeat that 10-minute on/off cycle six times to equal one training session.

Hypoxic Silo


Physiologically, this process creates a temporary state of hypoxia (low SaO2), which stimulates your body to release a hormone called erythropoietin – otherwise known as EPO – which stimulates the increased production of red blood cells. If you were to take synthetic EPO, you’d get busted, and if you inject extra red blood cells that’s called doping, but increasing your red blood cell count through the IHT process is fully within the rules. Over the length of the program, you gradually go down to lower and lower SaO2 levels during the six-minute cycles; my training program had me bottoming out in the mid-70% range, which is comparable to the oxygen percentage at 20,000’.

Increasing the number of altomixers simulates higher altitudes by decreasing the oxygen concentration of the air you breathe.

Without a doubt, the hypoxia state during the six-minute “on” cycle is real: during several sessions I experienced lightheadedness, lethargy, and headaches that would sometimes linger after I was done with the session. It’s also common to have general fatigue during your first week of ramping up the sessions, so you’re advised to back off the intensity of your physical workouts for a few days until your body gets the hang of the routine.

Aside from the physical side effects of intermittent hypoxia, the whole process is fairly user-friendly; there aren’t many other ways to get a training benefit while sitting in front of the TV. The only maintenance that is required is moisture management in the tubes, filter, and altomixer units as your exhaled breath undergoes condensation. Many of your 4-minute rest periods will be spent draining out the air tube or squeezing moisture out of the soft products before starting the next round. Otherwise, the primary limitation to the system is the life span of the hypoxic silos, which have a short duration of effectiveness at absorbing CO2. The AltoLab user guides say you can typically complete 2 to 3 sessions (one hour per session) with a single silo before it needs to be changed; during my training cycle the average ended up much closer to two. You can stack one silo on top of another to extend the life span of the old unit for another half-session or so, but the effectiveness drops off rapidly. My 8-week training program included 27 total breathing sessions, and the ULTRA kit comes with 6 silos, but I ended up purchasing four more silos (10 total) in order to finish all 27 sessions with the parameters that the program called for, even with extending the lifespan of each silo as much as possible.

Now for the key question: does it work? From my experience, yes… and maybe. I should preface this by saying my experience is a sample size of one, which could be impacted by numerous other variables. Also, my observations are completely anecdotal, and not based on any laboratory testing of VO2 Max, hematocrit and hemoglobin counts, lactate threshold, or any other performance parameter. However, here are my key takeaways from using AltoLab in conjunction with my training buildup to Hardrock.

Most noticeably, aside from the first week of breathing IHT sessions where I felt generally sluggish, the volume of physical training that I was able to maintain was noticeably bigger than anything I’ve sustained before. Compared to other training cycles for 100-milers, my overall mileage this year was about 20% higher than normal, my overall vertical gain was about 150% greater than usual, and I was able to consistently use cross-training two or three times per week. I was able to maintain this routine from one week to the next with one rest day per week, and my body tolerated all the activity without breaking down (injury) or burning out. It is probably pertinent that the vast majority of my training was done at low intensity that’s generally easier to recover from on a daily basis, but it was a great confidence boost to roll from one workout to the next without needing large blocks of time to recover in between.

As for the event itself, during my nearly 48 hours on the Hardrock course, I was fortunate to only experience very minimal symptoms of altitude sickness; I had a low-grade headache towards the end of the first day, and a mildly unsettled stomach during the second day and night. I didn’t have any serious lightheadedness, hyperventilation, lethargy or problems with kidney functioning. In general, I was able to maintain a slow but consistently steady pace throughout the event, kept very even splits and maintained my relative position in the field consistently from each aid station to the next, and never felt like I was in crisis mode in terms of my body giving out on me.

On the other hand, the altitude at Hardrock was definitely a limiting factor in my performance, and contributed to a much slower pace than I anticipated. It hit me pretty predictably somewhere between 11,000’ and 12,000’ on each pass, where I simply lost the ability to maintain a steady pace, and took far more walking and/or standing breaks than I thought I would need. To be fair, I’m not really sure what I expected in this regard; I knew I wouldn’t exactly run like Kilian, but I also thought I’d stay closer to the pace that I held on training runs in California and tune-up races in the Sierra Nevada Mountains. Perhaps this was just naïve and wishful thinking from a Hardrock newbie.

In the final analysis, I accomplished my goal of finishing Hardrock for the first time, and I’m fairly certain that using the AltoLab ULTRA kit contributed to that result, but to what degree I’m not certain. It’s completely possible that I would have had a similar physical experience and performance result without using it; after all, I did train like a maniac, and there’s certainly no substitute for that. It should also be noted that I traveled from sea level and arrived in Silverton literally less than 24 hours before the race, which most physiologists believe is the second-best approach to high-altitude events if you can’t spend a full two weeks acclimating in advance.

Even though AltoLab is a relatively affordable option in comparison to altitude tents, it’s still not cheap – especially if you want to use the system on an ongoing basis or for a buildup of more than a couple of months. If the price tag is within your comfort zone and you want to give yourself every possibility of success, I’d certainly recommend the AltoLab system as part of your overall training regimen for a high-altitude bucket list race.


About Author

Donald is a physical therapist, California native, barefoot aficionado, and father of three with more than 25 years of experience in endurance sports. He was a collegiate rower at UCLA, then dabbled in marathons and Ironman-distance triathlons before falling in love with ultras in the early 2000s. His favorite locations to run include Marin County, CA, and the Sierra Nevada mountains, and he loves exploring America's National Parks. When he's not training for ultramarathons, he enjoys hiking or slacklining with his family in Monterey County, CA.


  1. Gee, I am such a Luddite. I trained for Hardrock the old-fashioned way 10-17 years ago. At sea level, I did repeats of hills to get 10, 000 – 12, 000′ of gain and the same down in 30-40 miles, and then went to Silverton two weeks before the run to acclimatize. And it worked! With the AltoLab Ultra Kit, I could sleep in instead of doing long hard runs, and skip the acclimatization. What will they think of next? Virtual training and races?

    • Bud: Glad your method worked for you. The point of this is that not everyone can spend 2 weeks in Silverton before the race. The device is by no means a substitute for training; that was stated in the piece.

  2. I would really liked to have seen an actual test/proof of the results (VO2, red blood cell count, etc.) before a reputable source like UR mag would advertise this product as a featured review! Heck, the device came with a pulse oximeter! It would have been really easy to measure O2 levels and track changes over the 8 week trial! Maybe also a test to see if the same results couldn’t be achieved in a sauna or with anaerobic training? It takes several weeks for a trained athlete to acclimatize while sleeping for 8 hours a night in an altitude tent! Can this product produce the same acclimatization benefits? Unfortunately, this article didn’t prove it one way or the other! All I’ve read here is, “maybe it worked, maybe it didn’t”…

    How about a real test, UR? If this product actually works, there would be quantifiable results! I’m sure AltoLab would be thrilled to see UR prove that their product is legit! UR readers would win as well when they had more info to guide their purchasing decisions than, “Now for the key question: does it work? From my experience, yes… and maybe.”! Until then, that key question is left unanswered! I love you UR! Please do better work than this! You’re a great source of ultra running info!! Your readers deserve much better than “yes and maybe”!

    At the least, it’s awesome that it gave Donald the confidence he needed to train for and execute at HR100! Even if it’s mostly placebo, it’s great that he believes it helped! Congratulations on your finish at a tough event!!

    All Day!

    • Hi Ken. Thanks for your feedback. Even if I had access to a lab for legit VO2 Max and RBC testing, the results wouldn’t be scientifically valid – merely an “experiment of one.” And as you correctly pointed out, the only way we could have a control group was to have multiple people get into Hardrock (good luck with that!) and have some of them use IHT training and others abstain … but even then the evidence would be anecdotal. For what it’s worth, my resting SaO2 was 98-99% even before using the product, so an increased RBC count wouldn’t translate into a dramatically improved SaO2.

      The science on IHT training is out there; none of it is branded with a specific company’s product, but here are a couple of foundational studies:

      In regards to “advertising as a featured review,” we don’t have any relationship with the company or any obligation to present the product in a certain light. I was legitimately torn on whether using AltoLab made a difference between success and failure at Hardrock, and if I’m lucky enough to get into the race again, I’ll probably do without IHT just to see how it goes. Our reviews aren’t inherently endorsements; sometimes products are interesting to discuss even if they’re inconclusive.

      Thanks very much for the discussion!

  3. If you look at any real physiology research this type of device is such a gimmick and not worth spending a single dollar on. Even altitude tents don’t provide enough exposure unless you are spending 12-14 hours a day in them.