Eight weeks of simulated altitude training – part 2

I’m four weeks into this little experiment and all is well. I’ve completed all my scheduled sessions so far and I am definitely coping with the gradual introduction of intensity into the program.

In the first two weeks I completed six aerobic sessions primarily aimed at preparing my body for the more demanding intervals in the second half of the program. From week 3 I began one active recovery session on a Monday followed by a 6 x 5-minute interval session at threshold on Wednesday. Both these sessions were completed in the altitude chamber at Bodyology. On Fridays at home, using a portable altitude unit, I completed 3 x 6-minutes efforts done as blocks of 40 seconds hard and 80 seconds easy.

As you can see the program for the week covered a variety of intensities that targeted both aerobic and anaerobic energy systems. Through this program I’ve noticed some considerable changes in my perception of effort as well as my ability to ride at higher intensities.

I think one of the major points I quickly realised was that by consciously controlling my breathing to take deeper breaths I was able to keep my oxygen saturation levels a lot higher. I feel this also improves my ability to generate power during the harder intervals.

During my preliminary test at altitude, to set my training zones, we were alarmed at how low my oxygen saturation was. In retrospect I believe the low values were due to that fact that my breathing was very shallow as since then I have been able to stabilise the values at higher levels just through breathing deeper.

As described in part one of this three-part series I completed a few simple preliminary tests in an attempt to track any possible changes in body composition and physiological capacity over the eight-week training block. As I didn’t control training outside of the altitude sessions or, more importantly, employ a control period as a reference I will not be able to make direct links to any observed changes. However, I hope that the tests I employed will give some insight into the possible tests that could be used to monitor physiological and performance changes in a more extensively controlled study.

To monitor anthropometric changes we measured my body composition using the BOD POD system at Bodyology. To test aerobic capacity I completed a cycling VO₂max test, which also defined my power at VO₂max (PPO). As a test of anaerobic capacity I chose a time to exhaustion test at 150% of my PPO. This test requires a mix of aerobic and anaerobic energy systems but is a good measure of changes in lactate buffering capacity, which is one of the more recently reported benefits of simulated altitude training.

My baseline altitude session also allowed us to set training zones based on my heart rate and oxygen saturation at various intensities. Below I’ve presented all the results to date and I will add the final results in the next installment once my training block is complete.

I am still surprised by how much my power output is reduced while in the simulated altitude training chamber. I knew from the start that this would happen but I haven’t experienced it to this degree while racing or training up at Falls Creek or Mt Hotham.

My sustainable numbers are close to 30% lower than I can hold at sea level. My 6 x 5-minute interval sessions were supposed to be completed at threshold heart rate, which for me is 178 bpm (at sea level that is 330W).

In the first week I struggled to get my heartrate beyond 150 bpm. However, as the program has progressed I’ve been able to push a little harder and now, after three weeks of intervals, I am slowly able to get closer to my target numbers. I’ve included a table of my intervals to show the improvement over the weeks.

The interesting part of this is that the limiting factor doesn’t appear to be metabolic. For example, in the first week of intervals my breathing was still controlled and the sensation in my legs wasn’t that of ‘burning’ as you’d usually expect but more of an ‘emptiness’ and an inability to generate force.

It was more as if there was a central mechanism within the brain that wouldn’t let me push any harder. Only now in the third week of intervals am I able to push hard enough to get my HR up close to the prescribed levels, suggesting the mechanisms regulating intensity are adapting and setting new ‘safe’ working intensities. I may be way off the mark and the physiology behind it may be far more complicated but subjectively this is how it feels.

One point that has come up in conversation a few times with others who have undergone simulated altitude training is either an increase or decrease in hunger in the hours following the sessions. Due to the higher metabolic cost of hypoxic (i.e. oxygen-poor) exercise it is thought that it may have some influence on appetite. I haven’t really found a notable change.

I complete my sessions between 06:00 and 07:00 and always consume my usual breakfast after each session then resume normal eating throughout the day. I must admit though I have been consuming a few extra calories of late. However, this time of year (winter) I always find myself eating a little more than usual.

I’m still continuing to learn a lot from this experience and looking forward to reporting the end test results. Along the way I’ve been testing as many things as possible and there is still a lot I’m yet to understand about how the body reacts and adapts to hypoxic environments.

I will follow up with a few more observations as well as my final test results in my final report in a few weeks’ time.