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Get High and Get On Down ! Part II

IHT in Practice


To establish how Mark personally coped with hypoxia we tested him by getting him to breathe 11% oxygen, timing how long it took for his SpO2 to de-saturate to 83%.We then measured his recovery time. These two figures give a good description of the state of the individual and reflect the mechanisms they exploit to cope with hypoxia.

Marks results (Fig 2.) are quite typical of a normal healthy person. I must admit I was expecting some extraordinary results, but in fact Mark is quite normal.


Fig 2.

Hypoxic Test Pre IHT – 11% O2. Measuring Saturation Percentage of O2 and Heart Rate

The graph shows heart rate (red line) and the saturation percentage of oxygen in the blood, SpO2 (blue line). As you can see, heart rate rises in response to the reduced oxygen. It took Mark 113 seconds for his body to reach 83% de-saturation: this is quicker than during the breath holding exercise (Fig 1) due to absence of CO2 build up. Mark displayed a 2- stage recovery before his saturation percentage returned to normal. On the basis of this test we were able to set Mark a suitable training protocol which would improve his tolerance to hypoxia and his recovery speed.

Marks first training session took place on a Monday. We set Mark up with a protocol of breathing 5 minutes of hypoxic air (12% O2) and 5 minutes of ambient air

(20.9% O2). This would be sufficient to achieve 83% oxygen de-saturation every 5 minutes, whilst providing enough recovery between the hypoxic cycles.


 Fig 3.

Session #1 – 12% O2. Measuring Saturation Percentage of O2 and Heart Rate

The results of Marks first session (Fig 3.) were varied. As you can see, the SpO2 (blue line) was quite spiky and random in its mode of descent, and it also dropped below the desired 83%. I soon realized Mark was using his own techniques to try to beat the machine! Well, resistance is futile –the machine cannot be beaten. The techniques Mark was using were buying ( or more precisely, renting )him a little extra time, but the subsequent debt he was having to repay was making his Sp O2 levels drop below the desired 83% and having a detrimental effect on his recovery phase.

These first few sessions proved very useful for Mark, he was able to see the effect of Skip breathing, Belly breaths and mental focus on his oxygen saturations. Mark describes it thus:

"Sessions have been interesting, albeit somewhat surreal. The challenge has been to produce a consistent profile for each period on the Hypoxicator. I noticed that I seemed able to control my saturation percentages by means of my my mental state. A relaxed, ‘zoned-out’ phase at the beginning kept my saturation levels high (a bit too high for efficient training benefit), and a more focused alert phase mid-way through helped sustain whatever level I had dipped to."

Now Mark had to let the machine take control of the session, rather than trying to control the machine. This would allow for a greater training effect, enabling Mark to maintain the desired SpO2 for a greater duration of time whilst having a smoother recovery phase.

Mark soon mastered this technique, and over the days, as Mark acclimatised we were able to reduce the amount of O2 he was breathing during the hypoxic phase from 12% down to 9%

The final session of the 3-week course showed some great results (Fig 4.). Marks de-saturation phase was extended and maintained at the appropriate levels. His recovery had changed to a one-phase rapid ascent and he was able to maintain consistent healthy O2 saturation during the recovery phase, which indicated that his body had adapted to the oxidative stress associated with the induced hypoxia. 


Fig 4.

Session #15 – 9% O2. Measuring Saturation Percentage of O2 and Heart Rate

Final Results

After Mark had completed his course he returned the following Monday to do a repeat of the benchmark hypoxic test we conducted at the beginning of the 3-week IHT program. Mark was asked to breathe in a similar manner as during his first test. The results (Fig 5.) show a dramatic improvement in Marks ability to buffer the effect of hypoxia and to speed up his recovery. There was no lag in recovery, which was now one phase and rapid.


Fig 5.

Hypoxic Test Post IHT – 11% O2. Measuring Saturation Percentage of O2 and Heart Rate

Marks buffering capacity, measured by the time to decent (Td) improved 48% from 113 seconds to 167 seconds. His recovery improved a staggering 122% from 80 seconds to 36 seconds.

Mark also noticed a difference in the gym:

"At the end of the first week", he observed, "I put my training benefits to the test. An hour on an exercise bike. The first 30 minutes on a variable resistance profile found me unable to get my pulse above 130 bpm."

Mark continues: "The second 30 minutes I felt more energized, and was up to 145-150 bpm (normal for me)."

IHT has been found to lower heart rate both at rest and during exercise, reflecting greater stroke volume with improved efficiency.

The final test would come at the end of the 3-week training period. Mark would do a dry static apnea. As he describes it:

"This morning I had a go at the final test of the IHT training – a dry static. Despite still suffering with a head cold. I managed a series of holds – 4m, 5m rest, 5m hold, 6m rest, 7m hold."

"My previous PB was 6m30s, so I’ve improved by 30 seconds. Not only that, but I had no indications of LMC (Loss of Motor Control). I felt I could have gone further still, but felt that 30 seconds was a significant enough jump."

"Seven minutes would represent a 46-second improvement on the current UK record, so all I need to do now is repeat the same thing in a competition! This test, along with the other measurements you have taken, indicate to me that the IHT has made a significant difference to my apnea abilities."

What caused these improvements? We did a simple blood test to measure Marks haemoglobin levels. Mark provided me with the results from a test he had done a couple of weeks prior to our training. The results I obtained were consistent with his previous results. In Marks case IHT did not boost his haemoglobin levels. Marks red cell count is normally fairly low, which makes his blood quite thin – a contributing factor to his low blood pressure. However the red cells he does have are packed full with haemoglobin, indicated by high MCH and MCHC levels.

Everybody responds differently to hypoxia. Whilst some people produce more EPO and consequently more red blood cells, others stimulate the pro-oxidant system in the body making it more efficient in other ways. No one fully understands how the body adapts. One thing is sure, though: Mark Harris was able to increase his apnea times, tolerance to hypoxia and improve his recovery from the oxidative stress involved in freediving.

IHT courses can be booked at The Altitude Centre from £249. They also sell personal IHT machines to use in the home from £369. To find out more visit  or call on 0870 950 4479.