Not sure about what your dive qualifications are but I am a diving and nitrox instructor
We are clearly instructed to tell students what the benefits of nitrox are and we say that the proven one is extended bottom time and as consequence reduced risk of DCI.
I Don't see how this has any relevance to the discussion. You're a dive instructor, not a scientist. Of course you tell your students what you've learned.
All others ideas like yours are theories that have no back up, if they did it would end up in the training material but to date this has not happened.
No need to repeat yourself here. I think we both know there are no studies to back up the claim that nitrox reduces fatigue in recreational diving. BUT from what our physiology tells us about how our body responds to increased oxygen during activity, there is reason enough to make an educated guess about what I experience and what the actual correlation is between Nitrox and fatigue, it just hasn't been tested in a sound study yet.
For your information there are also other theories that say that increased oxygen level actually brings more free radicals and aging and fatigue, again nobody is going in depth there as nobody wants to know if that is the case
There have been lots of studies that make a correlation between an increase in oxygen and the introduction of free radicals in the body, which, over time, can expedite the aging process, etc., but this also has little relevance to the present discussion.
The rubicon test were not only psychometric they also looked at symptoms of fatigue if you read it carefully and a test on 10 is more significant that no test. Where is one single study that proves nitrox reduces fatigue? I would love to read it.
The testing was conducted in a dry chamber, not in the ocean. 11 divers is simply too small of a sample to make any conclusions from a single study There are no tests that prove fatigue levels are decreased by Nitrox, but according to the study "it is extremely common for divers to claim less fatigue following a dive breathing EANx then they would expect for a similar air dive"... this is why the study was conducted.
Test methods used were Visual Analogues scale and MFI-20 which rely on SELF REPORT SURVEYS from the subjects. They justify this as being the best possible way of testing because fatigue is self reported. In the study no one reports feeling less fatigue. Yet in the real diving world you have an extreme amount of divers claiming less fatigue. Both are based on self reports. How does this prove anything?
You know what might be helpful? Testing people who actually claim they feel less fatigued, or testing a larger population sample in a real-world dive setting along with physiological tests like blood and tissue sampling, to cross-examine the self reports.
What's funny to me is that in the discussion section it says "It is possible these tests may not be appropriate for measuring acute change (before and after the dive). The mfi-20 has not been used in this fashion and subjects may have remembered and duplicated their pre-dive answers to some extent."
Wow, so the only real thing to conclude from this study was that it was a waste of time and money.
The psychometric (concentration) portion of the testing was consistent with previous reports of testing in a real world dive setting on regular air; no significant changes before or after the dive were found. So if there were no changes on normal air, and they know this already, why would there be changes on Nitrox? No one is claiming that nitrox improves attention and concentration skills, or "working memory". All I'm saying is that I feel less physically tired, and have more energy to keep going on a multiple dive day. Maybe they should try testing for muscle endurance/fatigue as well. It was just assumed the reported fatigue would be associated with psychological conditions instead. Which may be a contributor in some people, but how will that ever be determined if you only test 11 HEALTHY DIVERS (well, 2 with colds) IN A DRY CHAMBER?
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