View Full Version : Oxygen "debt"

Bert Petersen
January 25th, 2003, 04:55 PM
I have always thought that one cannot store O2 in the body.How is a "debt" created then?? It seems to me that a better description would be "Oxygen need".......
Some of us are puzzled by the following questions:
1. At what point during a short race does the discomfort of not breathing become a real need ?
2. We all know that you can swim faster at free and fly without the breathing process interfering with our stroke. We also know that swimming a longer distance requires a constant O2 intake. Is this a time thing or a distance problem ?
Emmet, and others, weigh in here will you ??


Damage Inc
January 27th, 2003, 08:30 PM
It has been a few years since my last pulmonary phisiology class, but as I recall, and see in practice, the main stimulous to breath is the accumulation of carbon dioxide (CO2) and not the lack of O2. Very deep in the brain is an area that controls breathing, and when CO2 accumulates in circulation, it increases hydrogen ions which stimulate this respiratory center, causing us to breath. The brains main desire is to eliminate CO2 first. Sure the muscles need O2 for metabolism, but that feeling of "air hunger" is most likely due to the high levels of CO2 produced during exercise stimulating the respiratory center. The best way to get rid of this excess CO2 is to take slower deeper breaths, not fast little ones.
I don't know if this answered any of your questions, but I thought I would throw in my 2 cents.
Any one else?

jim thornton
January 27th, 2003, 09:44 PM
I think this essentially boils down to which energy system is primarily being used. In all out sprints lasting in the vicinity of 10 seconds or less, such at the 100 yard running dash (well, for me, make that the 35 yard dash-waddle), breathing doesn't matter for performance because the muscles are being powered by the anaerobic respiration system (i.e., fermentation.)

In very long events, such as the marathon, the vast majority of muscular activity is fueled by the aerobic system, which, as its name suggests, requires air.

Swimming doesn't have events that last 10 seconds or less (unless you count the 25 yard sprints in our Y league), so even the shortest official events tap into at least a little bit of the aerobic system along with the anaerobic system.

However, it seems to me that it takes time for oxygen in the lungs to make it to the muscles, so when Anthony Ervin does his 19 second 50 yard sprint, I suspect air breathed during the race itself does not reach his muscles in time to do any good--hence the lack of taking many (if any) breaths. On longer sprints, like the 100, then oxygen probably does have enough time to circulate to the working muscles, so you wouldn't want to avoid breathing here!

Even during 50s, sneaking a breath or two during the race will make you recover faster after it's over--and in the case of some of us older fellows, perhaps help guard against premature demise.

In terms of the CO2 being the stimulation of the urge to breathe, I had this demonstrated last summer in Colorado when I was working on an article on altitude sickness. I went into a hypobaric chamber, went up to a simulated 18,600 feet (i.e., Mt. Everest base camp), and with a pulse oximeter had my blood oxygen saturation level measured at 71 percent. (Normal at sea level is 98-99%). I felt fine--absolutely no sense whatsoever of being at all oxygen deprived, despite the fact, as one researcher told me, that if I had showed up at an emergency room with 71 % ox sat, they would have rushed me to an intensive care unit.

Later, when I emerged from the chamber and was more or less normal again, I tried to see how low I could get my oxygen sat level by holding my breath. After a minute and 15 seconds, I only got it down to about 93% (I was in Boulder, so my baseline was 96% at this altitude), but it felt awful. I am sure the accumulated CO2 was responsible for the overwhelming urge to breathe; in the chamber, I was "blowing off" CO2 with each breath I took of the thin Mt. Everest-base-camp like air, so there was no accumulation to make me feel miserable...

But this is a digression. What was your question?

Just joking. My best advice: breathe as much as you want in 100s and longer; take zero breaths on 25 sprints (if your league ever has these); and one breath up, two back maximum on most 50s.

Bert Petersen
January 29th, 2003, 10:35 AM
Thank you, Barry and Jim, for the info on CO2.........I never thought of that. But it does help explain why you feel discomfort way before you really have a physical need.
However comma, I still have an unanswered question, to wit: at what point, be it time or distance, do we meet that old devil "oxygen debt"? On a straight swim, is it after 30 seconds ? After 25 yards ?
Let me explain the motivation for the question : As some of you may know, I am and have always been a flyer. My other strokes pretty much stink. Still, I am sometimes seduced by the dark side and I enter an IM event. What precipitated this question of O2 debt was a comment by a well-meaning young Coach after my most recent 100 IM. "Bert, you need to breathe more than once or twice on that first length of the IM because you are putting yourself in 'oxygen debt'." He went on : " when you pushed off on the backstroke leg, your face was beet red "
Now, since I thought I new better, I began to question this advice. Here is why : After 20 years of pounding out 50 fly races, I have learned through trial and error that each breath costs me .30 seconds. Since I would rather win than breathe, I suffer through the discomfort. But I also know that this trick doesn't work on a 100 because (I guess) of Oxygen debt. Too much is too much, and this is exactly why they made breast-stroke a surface stroke. Anyway, we're focusing here on an IM...
1. I feel no discomfort after a 25 fly without a breath, especially knowing that the "breathers stroke" is coming next.
2. If my face was red, it was probably out of shame that someone might actually see me doing backstroke.
3. I had my best time in 4 years !!!
So, please, tell me exactly at what point in a race, time or distance-wise, can I expect to encounter this O2 debt monster ?

jim thornton
January 29th, 2003, 11:21 AM

I think the answer to your question is time, provided you are giving it your maximal effort. If you swim comfortably below your lactate threshhold, you can go all day. However, if you are doing an all out sprint, the demands on your muscles are so great that they burn carbs in the absence of 02, in the process giving off lactic acid (that horrible stuff that makes you whimper in the water!) I read some place that this all-out anaerobic effort can last only 8-9 seconds before you produce enough lactic acid to compromise your continued performance.

Eventually, you will also start burning fat in the presence of 02, which is a much more efficient energy system (aerobic), and much more sustainable for long term performance.

The 100 IM is one of the many gray zone events: if you don't work hard enough to generate a miserable degree of lactic acid, you won't get a good time. But if you all-out sprint from the get go, you may well generate so much lactic acid too soon that your limbs turn to tungsten by the middle of the 3rd length. It's hard to paddle with tungsten oars!

I think your coach is right in advising you to take a couple breaths on the first 25 fly. yes, this will slow you down a bit in the beginning. But it will help ensure that your system has at least some oxygen circulating in your blood stream when you've exhausted all "anaerobic fuel" and need to switch to predominately aerobic fat-burning in the latter lengths.

I apologize to the exercise physiologists out there is some of this is overly simplistic. Bert, if you want to read a sensational book, check out Brian Sharkey's Fitness & Health (Human Kinetics) at your library. A superb explanation of how the body's various energy systems work, how to optimally train them, etc.

Bert Petersen
January 30th, 2003, 03:14 PM
I must have read a dozen articles by now regarding this topic.
Bottom line for this flyer : Breathe on demand, pay debts later.