Eight weeks is up and it seemed to fly by. It’s time to sum this whole experience up. Did it make me faster? What were my subjective findings during and after these 24 hypoxic (reduced-oxygen) sessions?

It has been a big learning curve. I will admit I still understand very little about this method of training but my interest has been sparked and I’m now dreaming up studies I can do to better understand the effects and benefits of altitude training.

First I’ll run through my pre- and post-program BODPOD testing. As a reminder, the BODPOD system can be used to determine your body composition, including the percentage of body fat and lean muscle you have.

There was really no major change in any of these numbers (see Table 1 below). We didn’t control for my diet or training so it is hard to say either way if the hypoxic sessions were the cause of the small changes.

Although I didn’t see any major changes under these conditions the BODPOD is a very simple and accurate way to track changes in body composition. For example, we all wouldn’t mind losing a little bit of fat mass. However, if not done correctly it can result in significant losses in fat free mass, primarily muscle.

This can result in a significant reduction in power output and performance can be negatively affected as a result. The BODPOD measures both and can track the changes in different body tissues making it a valuable tool to a dedicated athlete.

Table 1: Changes in body composition

Table 1: Changes in body composition

As you can see from Figure 2 and Table 2 below, the post-altitude-training step test showed a good improvement on the pre-training step test. (As a reminder, the step test involved increasing the power output throughout the session to test blood-oxygen saturation levels at different power outputs).

As I mentioned in my first article the guys at Bodyology and I were very surprised at how low my oxygen saturation (SaO2) dropped during first time in the chamber. It was alarmingly low and if it had remained that way I would probably have been doing supervised sessions to ensure my safety.

If you keep in mind that 80% SaO2 is deemed the ‘safe’ lower limit, I started and ended below that! However, I quickly learnt that controlling my breathing elevated the values and as you can see in my post-altitude-training test numbers, my SaO2 remained significantly higher throughout.

Did this make a difference to my performance both in and out of the chamber? Yes, I believe it did.

The step test showed that training in simulated altitude not only improved my oxygen tolerance but also marginally lowered my sub-maximal heart rates by about 5bpm at any given workload (see Figure 2 and Table 2 below). I can’t discount daily variation in heart rate but this is the direction and also the degree of change I would expect to see.

I think one of the other main points was that in my final stage at 300W in the pre-training test I was cooked and had nothing left in my legs. In the post-training test I was still OK and felt as if I could have continued. I think this ability to push harder with reduced oxygen availability is one major adaptation that occurs, as discussed in my second article through the observations during my interval sessions.

By the end of six weeks of intervals (I didn’t start intervals until two weeks in) I was holding nearly 40W more for each five-minute interval. I think this is proof enough that either metabolic or neural adaptations occurred.

Figure 2: The effect of simulated altitude training on power output and blood-oxygen saturation. The dashed blue line (pre-training oxygen saturation) and green line (post-training oxygen saturation) show that Stephen was able to maintain a greater concentration of oxygen in his blood for a given power output. The solid red (pre-training heartrate) and purple (post-training heartrate) lines show that for a given power output, Stephen's heartrate dropped as a result of the training.

Figure 2: The effect of simulated altitude training on power output and blood-oxygen saturation. The dashed blue (pre-training oxygen saturation) and green (post-training) lines show that Stephen was able to maintain a greater concentration of oxygen in his blood for a given power output. The solid red (pre-training heartrate) and purple (post-training heartrate) lines show that for a given power output, Stephen’s heartrate was lower as a result of the training at simulated altitude.

Table 2: Data for the above figure

Table 2: Data for the above figure.

Onto the laboratory performance tests (see Table 3 below). I found no major change in values for VO2max (maximum oxygen consumption) or power at VO2max (PPO) nor did it feel any easier or harder during the test (it just hurt as usual!)

In saying that, I really didn’t expect to see any major change either. I’ve done more VO2 tests than I can remember and my values have never really changed too much when I’m at a decent level of fitness.

Most studies investigating the effects of hypoxic training don’t report any major change in VO2max or any markers of O2-carrying capacity in the blood, especially in already-well-trained subjects.

That said, I believe it may increase values in individuals who aren’t at an elite level, as moderately-trained individuals appear to be more responsive to such a stimulus.

One of the most interesting results came from my time-to-fatigue effort at 150% of my power at VO2max (150% PPO). For this test I set our fancy bike in the lab to a constant power, which is independent of cadence and how hard I push. The bike just holds the power and I gradually fatigue until I can’t turn the pedals anymore. Yeah, it hurts as much as it sounds!

In the pre-test I lasted 83 seconds; in the post-test I lasted 87 seconds. This doesn’t sound like much of an improvement but it is actually a 5% increase in time-to-fatigue. It still hurt the same but I think that a 5% improvement in anaerobic capacity is a good gain.

Some recent evidence suggests that hypoxic sprint training can improve the muscles’ ability to clear and buffer lactate. One study of note revealed good increases in repeated sprint performance after just eight training sessions over four weeks.

What is interesting about my improvement is that I really didn’t do any specific efforts that aimed to increase my anaerobic capacity. I spent the entire eight weeks of training both in and out of the chamber doing longer sustained aerobic efforts as I was in an aerobic build phase of my training.

I’m really only now starting to incorporate above-threshold sessions to begin to ramp up to some of my bigger goal races in a few weeks’ time. So the periodising of the altitude sessions within my overall training plan possibly came a little bit early. I really think a short block of simulated altitude training closer to a key event is more appropriate and would probably reveal more measurable performance gains.

Table 3

Table 3: Changes in laboratory performance tests.

So it’s time to wrap up this experience and bring to light some of the changes I’ve seen in my fitness and performance over the past eight weeks. Firstly I’ll start with my changes in fitness.

My performance tests really didn’t show a great deal of change in my physical capacity. However, I really think this was mainly due to the fact that I already started with a decent level of fitness. The demands of and physiological responses to simulated altitude training have been shown to elicit good changes in performance but not necessarily measurable physiological variables like VO2max.

I feel as if it has improved other variables like my muscles’ ability to buffer lactic acid, which in all reasoning should provide significant performance benefits. My time-to-fatigue test is indicative of that.

On the road training and racing I do believe the sessions have helped. I’ve had some pretty decent results in recent time trials and I believe the altitude sessions have contributed to that. One factor is my breathing.

The altitude sessions have forced me to consciously control my breathing. Now in races I find myself focusing on this and feeling significant reductions in perceived exertion when I begin to control it. Whether this is elevating my blood SaO2 like I’ve reported in the altitude step test or whether it’s just a more efficient way of breathing I’m not certain but it definitely helps.

In the last two weeks I’ve begun to lift intensity within my training and incorporate some shorter anaerobic efforts. My power numbers have surprised me on several occasions. Even though I haven’t been doing any specific high-intensity training I am hitting numbers close to what I have previously achieved after a good block of anaerobic type efforts.

I believe there have been some metabolic adaptations within my muscles and possible neural changes that have occurred that I haven’t really tapped into yet.

All in all this experience has led me to believe that simulated altitude training does have a place in a periodised training program. I think the biggest benefit would be done as a block of training in the final weeks leading up to a goal race, particularly if the race is at altitude. I will definitely be planning another block of simulated altitude training leading up to my annual Tour of Bright campaign.

Hopefully this year I can go one step further up on the podium with a little extra help of some specific efforts in the chamber. I also think that in combination with the use of an altitude tent and some extra hours spent sleeping at altitude significant improvements in blood parameters resulting in an improved aerobic capacity would occur.

I think the changes in blood parameters and aerobic capacity noted in the research are due to the longer hours of exposure when training and living at altitude and a simulated altitude tent would make a good substitution for this.

I’ll finish up with a big thanks to Michael, Andy and Ben at Bodyology. The facilities there are first class and so is their expertise. If you are serious about improvements in performance and are familiar with the new ‘marginal gains’ theories going around at the moment you would understand that small things count and simulated altitude training is definitely an avenue that you should explore.

Lastly thanks to David at Altitude Training Solutions (ATS) for the loan of the home-based altitude unit. If you haven’t got the time to get into a chamber the portable units (which can be hired from Bodyology or ATS) are just as effective as the chamber but provide a far more convenient option for the time-poor athlete.

It’s been a terrific experience and I hope I’ve shed some light onto the performance and physiological gains possible with this newly emerging training aid.

You can read part 1 of Stephen’s three-part series here and part 2 here. Thanks to Stephen for taking the time to do the training and write about it for us. If you’d like to read more of Stephen’s work, check out his great blog Human Performance Technologies. Thanks to the crew at Bodyology for providing Stephen with the eight-week block of simulated altitude training sessions. If you’d like a free one-week altitude training trial, contact Ben Griffin at Bodyology before August 31, 2013 and mention this article.