Nitrox!

[boulderjohn]

I do agree with you that there have been no solid findings however even a placebo can have positive effects. My thought process is that as long as the Nitrox is not doing you any harm, and you are not trying to sell it based on said speculation, then it is great if a person BELIEVES that they feel less tired after a Nitrox dives.

This is a purely non-medical or scietific opinion, but every once in a while a placebo can be a good thing.

While I agree with you on the placebo effect, I don't think it is a placebo effect. I think it is very real.

I am just cautioning everyone that no study has been done on this, and there is no known physiological explanation as to why this would be true. The fact that no study has shown it, and there is no such physiological explanation does not mean it is not true. It does not mean anything either way. It awaits further scientific investigation.

 

[DaleC]

I think you will find that increased O2 does not effect respiration rate.. as that is mostly driven by CO2 levels...and in many people.. the effect is to increase the respiration rate (slightly more available O2 = slightly higher CO2?)... but the reasons are not clearly understood.

On a cellular level, your post may be very true, but have not read any actual testing of this.

If we want to understand the effects of nitrox (oxygen enriched air) but lack studies related to diving it may be worth looking at other sports that have contemplated nitrox use.

Here is a portion of an article that discusses the effect.



Increased blood oxygen content is balanced by decreased flow

There is one oxygen-related problem which must still be surmounted, however: although the basic meet the muscles demands rationale for using oxygen during training seems unarguable, it has not stood up well to scientific scrutiny. In fact, one well-conducted investigation found that, although the breathing of hyperoxic gas mixtures did indeed increase the oxygen content of arterial blood, this process was perfectly balanced by a decrease in blood flow to the working muscles so that the actual amount of oxygen delivered to the muscles remained exactly the same(1). Through physiological feedback mechanisms, the muscles seemed to be saying: Thanks! The blood you are sending me is richer now, so I don't need quite so much of it. Let some other part of the body use some of the red stuff I've been consuming up until now?

Nonetheless, VO2max (the maximal rate of oxygen consumption) does increase by 2-5% when athletes exercise in a hyperoxic environment, and performances improve by up to 40% when athletes breathe pure 100% oxygen instead of the standard 21% oxygen air (2). How can these findings be reconciled with the fact that there is no actual difference in oxygen delivery to muscles?

There are various possibilities, but it is clear that increased availability of oxygen decreases pulmonary ventilation (the movement of air in and out of the lungs) and thus reduces the muscular work required for breathing(3), an effect which could lead to a significant improvement in athletic performance.



1. Perceived effort – the level of difficulty an athlete consciously assigns to a specific type or intensity of exercise – depends on a variety of physiological cues, including the degree of stress experienced by the respiratory system during the conduct of the exercise. If this respiratory stress is lightened, the intensity of exercise is felt to be lower, and an athlete will usually have confidence that he or she can perform at the given intensity for a longer period of time; 2. A reduced respiratory workload translates into a lower whole-body demand for oxygen during exercise (don’t forget that the respiratory muscles require oxygen during exercise too). Since the oxygen cost of exercise is reduced, an athlete will be operating at a lower fraction of VO2max and thus the duration of exercise can be increased, there being a direct inverse relationship between exercise sustainability and %VO2max.

I'll try to edit in the link (it doesn't seem to want to work right now.. now it does? let me know if it doesn't).http://www.pponline.co.uk/encyc/ergogenic-aids-can-increasing-oxygen-levels-improve-sports-performance-95

 

[Puffer Fish]

Dale, interesting article.. very professionally written... however almost all of the assumptions in it have proven to be wrong.. and if you look at his references and then look at the studies he has quoted... you will notice they don't match.

Back in the late 70's and 80's all of that was believed to be true... but if you check today, high performance athletes do training in exactly the opposite conditions. And as they can afford to do anything that actually works..

The concept of O2 limited does have it's place though, but only if one is at their maximum breathing rate, and is still O2 limited. Hopefully that is not the case with most divers.

As with even using air..if increased O2 reduced breathing rate, then at depth any experienced diver should see a lower sac rate....as we have millions of records measuring that... one would think it would have been seen by now.

For the record... at least for me.. on average, I show about a 5 -10% increase when using Nitrox on similar dives...just as I also show a decrease in SAC on the second dive, but nothing more after that. I know the increase is not that common... but it is not rare.

To test yourself you need two tanks, and a nice comfy chair...first make sure the regulators are the same and adjusted the same (helps to do the test several times with the regulators excchanged)..

Put the tanks behind the chair... get comfy for at least 15 minutes and have someone give you one to breath off of.. do at least 10 minutes.. then switch.. have the person mix up the order.. and not tell you.. also have them move the tanks around so you cannot tell which is which by hose position...do a couple of hours of this...then compare (you can use pressure, but it is nice if you have two computer to make something pretty.

Me, I go up.. my wife stays the same...and her sac rate is already way lower.. figures.

 

[wve]

I think one of the things that confuses people when the subject of Nitrox comes up is that we are talking about mixtures of gases.

I have to keep stressing to students that the reason we use Nitrox is not because we want to breathe more oxygen, but because we want to breathe less nitrogen.

Perhaps the fathers of Nitrox erred when they decided to refer to mixes by their oxygen content rather than their nitrogen content. When divers talk about using "enriched air" it gives people the impression that it is the higher oxygen content that matters most.

Instead of saying, "I'm using oxygen-enriched air," perhaps they should have said, "I'm using reduced-nitrogen air" -- kinda like "low fat" or "skim" milk.

No one breathes any pure gas for very long -- even oxygen -- without suffering harm. We were designed to breathe a mixture of gases. Thus one cannot really talk about the physiological effects of one element without considering the other.

To go back to the original question, when I use Nitrox, I do so in order to reduce nitrogen loading. My goal might be to reduce my DCS risk, to extend my bottom time, or both.

However, whenever I mess with the ratios of gases that I breathe, I must also keep in mind that there is another gas in the mix (trimix notwithstanding). If I decrease one, the other must increase. And that has consequences, too.

I don't really know whether changing the ratio of nitrogen to oxygen makes me feel better or stronger, or whether it affects my performance in any way. What I do know is that the very fact that I am diving makes me feel good, and anything that helps me to get underwater more often and stay longer is good.

 

[DaleC]

Dale, interesting article.. very professionally written... however almost all of the assumptions in it have proven to be wrong.. and if you look at his references and then look at the studies he has quoted... you will notice they don't match.

Here's another article (Book 2006) that echoes the first article. Read the top right hand paragraph on page 591. It even offers reasons why an increased O2 usage rate may occur.

Exercise physiology: energy ... - Google Book Search

Back in the late 70's and 80's all of that was believed to be true... but if you check today, high performance athletes do training in exactly the opposite conditions. And as they can afford to do anything that actually works..

I think you are refering to the practice of athletes training in hypoxic environments (high altitude) but positive results from that form of training are inconclusive. Most of the increases have to do with training that improves %VO2max. Long term hypoxic exposure increases the carrying capacity of the blood true, but that is a rather elaborate, but more legal, form of common blood doping.

(book 2008) Last paragraph of page 372

http://books.google.ca/books?id=zQGKmbg18J8C&pg=PA372&lpg=PA372&dq=does+breathing+higher+oxygen+levels+during+exercise+increase+performance%3F&source=bl&ots=y4ibzx6TDr&sig=VnAchuW6kZAIaLIjyjIZlzELikQ&hl=en&ei=vqUPSpmMCqWCtgOZlOH7Ag&sa=X&oi=book_result&ct=result&resnum=4#PPA372,M1

I'll edit in more supporting articles as I find them. I'm sure they weren't all written in the 1970's.

 

[boulderjohn]

I am finding this discussion on the effects of increased exygen very interesting, and I wish it were not at the tail end of a thread that is reallly on a slightly different topic. May I suggest that a new thread be created, possibly in the diving physiology section of SB? That way it would attract some new and knowledgeable participants who would otherwise miss it.

(My mind immediately spun to the use of hyperoxic mixes for decompression and the implications of Dale's position for that, and taking the discussion down that road would not be appropriate here.)

 

[Puffer Fish]

I am finding this discussion on the effects of increased exygen very interesting, and I wish it were not at the tail end of a thread that is reallly on a slightly different topic. May I suggest that a new thread be created, possibly in the diving physiology section of SB? That way it would attract some new and knowledgeable participants who would otherwise miss it.

(My mind immediately spun to the use of hyperoxic mixes for decompression and the implications of Dale's position for that, and taking the discussion down that road would not be appropriate here.)

Excellent point