As endurance athletes our one golden staple is oxygen. Without it we are reliant upon anaerobic energy production which would limit our exercise capacity to mere seconds before we are forced to stop and recover. At sea level the air we breathe consists of 78% nitrogen, 21% oxygen, and 0.04% carbon dioxide, with a few other inert gasses rounding out the remainder. However, as we venture upward the air becomes significantly thinner due to lower atmospheric pressure meaning the available oxygen is significantly reduced, for any given volume.

In Australia our Alpine regions peak out at approximately 2000m in altitude. In comparison, at the endurance-training mecca of Colorado USA, elevations of 3000-4000m above sea level are common. The greater the elevation the less oxygen is available in the air (while the absolute percentage of oxygen remains the same*). Simulated altitude reduces oxygen availability by removing oxygen molecules from the air as opposed to reducing the pressure that naturally occurs with increasing altitude.

Atop Falls Creek here in Victoria, Australia, at an altitude of roughly 1600m, the oxygen availability is the equivalent of reducing oxygen via simulation to about 17%. Climb to Pikes Peak in Colorado and the simulated equivalent drops to about 12%, making even the most trained endurance athletes gasp those extra few breaths.

Exercising muscle requires the continual supply of oxygen transported in the blood. At rest, in a healthy individual, the saturation of the oxygen carrying haemoglobin in our red blood cells is between 98-99%. As altitude increases the saturation of oxygen in the blood at rest is reduced and even more so when we begin to exercise. It appears that we are able to safely cope with saturation levels of about 80%, but it can get a lot lower than that.

The aim of simulated altitude training is simple: reduce the amount of oxygen available to the body so it is forced to adapt and become better at transporting oxygen to the working muscles. There is also the thought that altitude training stimulates responses that better equip the body to deal with harmful metabolic costs of anaerobic metabolism, such as the lowering of muscle pH (increased acidity).

Baseline testing

Like any good self-proclaimed mad scientist I was willing to subject myself to a few baseline tests so we could monitor any changes that may occur as a result of the simulated altitude training.

Before I commenced the eight-week altitude training block I completed a few tests at Bodyology and at my lab at RMIT University. Our baseline performance measures were a VO2max test to get an idea of maximal oxygen uptake as well as an anaerobic time-to-fatigue test consisting of an effort at 150% of my maximal aerobic power (power at VO2max).

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Andrew Garlick, the body composition guru at Bodyology, used the BOD POD body composition tracking system to accurately measure my body fat and fat free mass (essentially muscle mass) and to also get an idea of my resting metabolic rate. One of the reported effects of altitude training is a reduction in body mass as a result of the added metabolic cost of exercising in a hypoxic (oxygen-poor) environment. With these measures we hope to get a good idea of any changes over the coming eight weeks and I’ll share those initial results with you in the next article in this series.

The sessions

My program consists of me visiting the altitude chamber for a 60-minute session twice a week for eight weeks. I am lucky enough to also have access to a portable unit supplied by Altitude Training Solutions so I can do a third recovery-type session at home each week to ensure I gain maximal benefits from the training block. Having access to both also allows me to compare between the portable home face-mask unit and the commercial chamber system.

Ben Griffin, the endurance expert at Bodyology, prescribed the sessions for my training block. The first step before commencing any sessions was an initial test to see how my body responded at altitude. Individuals respond differently and the response appears to be independent of training status. It is important to get a good idea of each individual’s response so appropriate intensities can be prescribed throughout the program.

The chamber at Bodyology fits about five athletes. Currently there are three stationary bikes, two treadmills and just enough room to walk around the equipment. The chamber is set to simulate an altitude of between 3100-3300 meters. This results in an oxygen percentage of about 14%, which is definitely low enough to have an immediate noticeable effect.

Michael Chiovitti is the altitude expert at Bodyology and he ran me through my initial test. The main point of this was to determine my blood oxygen saturation levels at varying intensities so we could set my training zones and make sure I knew the intensity at which my oxygen saturation levels become critically low. Repeating the test at the end of the training block will give me another reference point to any adaptations that may have occurred.

Due to the lack of oxygen the heart rate versus intensity response is very different to that at sea level. When I push 200 Watts at sea level my heart rate is normally about 125 bpm. During the test it was about 20 bpm higher. Hence it was important to set my training intensities using heart rate and not my normal power zones as there is a big difference in capabilities compared to training at sea level.

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The first thing I noticed was how hard it was to sustain a conversation. As I was ticking my legs over and responding to Michael’s questions I found I had to momentarily stop talking mid sentence and take a few extra breaths. Even putting out 150W was feeling harder than usual.

My oxygen saturation levels were monitored using a pulse oximeter — a simple device that clips onto the end of your finger and monitors oxygen saturation and pulse rate by passing a light through the soft tissue of the finger and measuring the fractionated light that passes through.

With the initial test completed I was ready to start some serious training … or so I thought. The results revealed my blood saturations levels dropped relatively quickly upon commencing exercise to our safety point of 80%. Both Michael and Ben stressed it was important that we follow what is standard practice and complete two weeks of acclimatisation before we attempted any high-intensity efforts.

For the next two weeks I completed some steady-state efforts while my O2 saturation was continually monitored. I quickly learnt that consciously breathing deeper elevated my saturation levels and I’m now starting to lift the intensity of the training to see how my body responds.

Thoughts after two weeks

I must admit I was a little dubious at the start. I had read a lot of the literature about sleeping/living at altitude but knew little about the effects of training at altitude. My initial thoughts were that if altitude reduces your ability to perform quality high-intensity sessions then its benefits must be minimal or that it must take an extended duration to come into effect.

At this early stage I can report that I am already more comfortable while in the chamber riding at a simulated elevation of 3100 meters. Ive learnt that breathing doesn’t just take care of itself and by consciously focusing on my breathing I can increase my O2 saturation while exercising.

I must say I am looking forward to a few harder efforts and the reported sensation of breathlessness that results. After all, it can only make me stronger, right?

Time will tell. I’ll report back in a few weeks as my training block progresses.

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*The atmosphere contains the same percentage of oxygen at sea level as it does atop Mt. Everest however the air is significantly thinner as you go higher up. Therefore the amount of oxygen available is significantly reduced (i.e. you need to breathe in more to get the same amount of oxygen).

If you’d like to read more of Stephen’s work, check out his great blog Human Performance Technologies.