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Hypoxic training with oximeters

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Well-Known Member
Jan 21, 2004
Has anyone had much luck measuring their improvements in hypoxic performance through the use of oximeters? It would be nice to think that I could train and measure my hypoxic state on a stationary bike or step machine and see the improvement over time.....does it work like that?

eg (something like)
week one
- distance on stationary bike 0.5km
- time 1:30
- oximeter reading at end 91%

week five
- distance on stationary bike 0.75km
- time 2:00
- oximeter reading at end 86%


Eric F and others use oximeters for their static experiments, but I don't if they use them for dynamic experiments like this. I don't use one myself, though so I can't really say much.
JerseyJim did some experiments with dynamics while hooked up to a pulse-ox and he posted his observations on EastCoastFreediver. A copy of his post follows. Note that some of the observations seem relevant to recent discussions on this forum (CO2 compartment etc.)

I finally got around to trying apnea walking that everyone's been
doing. The track I used was from my garage down to the street and
back. That's 340' round trip. It started getting a little
uncomfortable 3/4 of the way through it. Think I counted 120 paces.
You can really feel the lactic acid in the legs the last few seconds.
It took about 1:10. The second time I tried it was easier. I had just
finished a 10 mile run an hour before, so don't know if that helped
or hurt.
By the way, I got my wife to bring home the portable pulse
oximeter from her nursing agency, and noticed interesting results.
Saturday the reading kept a steady 100% blood oxygen saturation, even
with shallow breathing. I want to note that the last 10 mile run was
2 days prior. Doing some statics, it took 3 minutes for the 02
saturation to even start dropping below 99 or 98%, even when
the "struggle phase" began. It seemed to really avalanche fast toward
the end, and my wife confirmed this is typical from charts she has
observed. I could not hold my breath below 72% saturation. I want to
mention how fast it began dropping. Once it dropped into the 80's,
the rate of decay was about 1% for each heartbeat, which happened to
be about 38 beats per minute at the end. The interesting thing was
that once I started breathing again, the reading kept dropping for a
few more seconds, then began climbing extremely fast, and the last
few percent (between 98-100%) took a few seconds longer, fully
recovering to 100% in about 45 seconds. The need for a longer
breathup must be to purge C02 trapped in the tissues and fat. (It is
claimed that fat tissue retains C02 and nitrogen 6 times longer that
other tissues). If I only had a method of measuring residual C02, it
would prove the other piece of the puzzle.
Day 2 (Sunday): Tested my 02 Sat. an hour after finishing a 10
mile run and washing the car. Could not get a "normal breathing"
reading of over 96-97%. This continued all day, although I could
breathe-up and force it to 100%. Note the day before, shallow
breathing yielded 100% all day. This reduction may have been
to electrolyte and mineral losses from a stressfull workout at 90% of
maximum heart rate, or maybe the apnea walking I performed that day.
This morning (monday) I still did not get a "normal breathing"
02 reading of over 98-99%. It seems apnea and hard workouts carry
over into the next day. I've suspected this from times that I dove
consecutive days at Dutch. The bottom times are never as good on the
second day of diving as the first day.
In conclusion, I suspect that the discomfort at the onset of the
struggle phase (that still indicated a 98% saturation), may be due to
C02 tolerance being low and not really low 02 at all. We all know how
practice can raise C02 tolerance, and now realize that practice will
improve that aspect. I haven't really practiced statics this year
like last year, so the C02 tolerance is probably lower than it used
to be.
Now if someone would develope a dive computer that has the finger
sensor attached (or wireless) to wear under the glove. That would be
the ideal diver "fuel gauge" that surely would prove usefull.
Especially if incorporated with an audible alarm, set to say 85 or
90% oxygen saturation.
Sorry for the long post, but the tests were long too, and I
felt I had to share them, so we gather a better understanding of our
physiology and our sport.
More tests to come someday,
Last edited:
Hi Pezman,

This is fascinating--even if I don't completely understand it yet. You say CO2 tolerance increases with practice? That's why I got 3:55 last night and the night before--and only 2's last week?
Wish I could exercise more--bet I'd get better--but snow's piled a mile high around here--or seems like it. Hubby and I go Mall walking, as much as we can--I don't drive, got epilepsy--and Handibus permission hasn't come through yet. Cabs too expensive...except for emergencies...anyways--I STILL GOTTA GET ME A NEW SWIMSUIT--I miss the water....
Any suggestions on "Frozen Water Dilemna" ....
Water Rat
Great post Pezman. This is so interesting I may have to get one of those gagets. How many seconds between starting to breath and seeing the o2 measure begin to rise? You mentioned that at about three minutes, o2 began to drop. How long past that before you had to breath?


Them's JerseyJim's words

Thanks for the credit, but Jersey Jim posted that on EastCoastFreediver. Hopefully he'll jump in and answer your questions.
I'm surprised that JerseyJim finds apnea walks or dives the day before to negatively effect dives/times the day after. I've always been happy to do apnea walks or empty lung tables to the point of samba the day before a big dive or static attempt. This approach doesnt seem to harm my performances. And I think I have read Erik Fattah saying he doesnt mind a samba the day before, and mentioning that other top static'rs do daily statics/tables for 3 weeks before a comp. If anyone else finds the same as JerseyJim please post. Thanks

I am only against "hard workouts" the day before a dive. My only cardio workouts were 15km runs. I believe they negatively impacted dives on the next day due to a great loss of hydration, electrolytes, etc. I'm not against dry apnea practice the day of a dive, or the day before. In fact I think it helps to raise the hematocrit, or keep it elevated. But a full day of diving seems to negatively impact the following day's dive possibly due to the renal diuresis I experience. I lose a lot of hydration from diving. I imagine we all do. That's evident by the popular "rubber-peeing" post :)

Pez, thanks for digging out that old post. I think it was from October. If I knew it would be posted here I would have tried to be more exacting and detailed with the results. Maybe even tested another day or two. There is some really good stuff being presented here. I hope we can put it to practical use.

Also, is that pic at the bottom of your posts of me? I think I remember that day from this past April. We were wearing two pairs of gloves that month. That wasn't even with your good camera. Not sure how the Apnios will perform in the colder months. Only used it from July to Oct.

It won't be long now.

I think you're right Jim about long dive sessions causing dehydration. And about taking a day of from cardio. Infact I decided last week that I would change my one day of rest to a friday(today) because Saterday is my regular dive day. Will see if I feel any stronger tomorrow.
Been reading two very interesting books, 'Swimming Fastest" by Maglisscho, and Tim Noaks' "Lore of Running" and both stress the need for tapers starting as early as 3 weeks before competition. For us freedivers who aim for low metabolic rates this rest period is proberbly even more important.


I think that the post is great, or I wouldn't have cross-posted it.

My signature picture -- Right day, wrong guy. That's Doug and I think that this was his first time out with the mono. You can kind of see the the front-mounted snorkel sticking out the front of his mouth.

As far as cameras are concerned, I think that some of the absolute best underwater shots that I've taken to date were with that cheap Cintar camera. The nice thing about the cheap cameras is that they are so simple that you can devote all of your attention to composition. Still, the 5050 is better all-around (although I'm still learning how to use the darn thing.
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