DevonDiver
N/A
Here's what seems reasonable to me:
- The typical recreational diver exhibits fairly lax skills and techniques; saw-tooth profiles, reverse-profile repetitive diving, relatively rapid ascents, short SI's, generally poor buoyancy skills, pushing NDLs, and has at best a rudimentary grasp of dive planning, tables, or their dive computers
- Lax diving skills - while unlikely to put the typical recreational diver in a chamber - are likely to produce sub-clinical DCS or so called "silent bubbles" in the blood stream and body tissues
- The silent bubbles from sub-clinical DCS that are experienced by typical recreational divers with lax dive skills are likely to produce symptoms of fatigue
- Accordingly typical recreational divers with lax dive skills who dive nitrox will experience less bubbles, and therefor will experience less fatigue secondary to the sub-clinical DCS they ordinarily experience when diving on air
But seriously, let's be more objective and consider it this way...
- The data from well-controlled studies (eg all participants are placed in a chamber or otherwise subjected to exactly the same dive profiles relative to depth, time, ascent rate, etc which are controlled by the scientists conducting the study) show that divers using nitrox have no statistically significant difference in post-dive fatigue as compared to divers on air
- Anecdotal "data" from poorly-controlled studies (eg: typical recreational divers jump in the water, do their own thing, and tell everyone "I feel better") suggest that those who dive nitrox are less fatigued than when they dive air
- So it would appear reasonable to conclude from the literature that people who dive in a well-controlled fashion exhibit less fatigue than people who dive in a poorly-controlled fashion... irrespective of their choice of breathing gas.
I agree 100%.
Nitrox doesn't make you feel "better" after a dive. But it can make you feel "less worse" after a dive where you'd otherwise off-gas inefficiently.
If inefficient off-gassing has become a 'norm' to the diver, then nitrox might be identified with reducing 'normal' post-dive fatigue (that needn't exist in the first place).
This assumes that nitrox use causes decreased nitrogen on-gassing for the majority of divers, due to dives being limited by air-consumption not no-stop limits (i.e. nitrox use does not permit relatively longer dives versus significantly decreased rate of on-gassing).
The consequence of that decreased nitrogen on-gassing is less severe sub-clinical DCS symptoms (fatigue) following an inefficiently off-gassed dive/ascent.
I doubt DAN's dry-chamber studies mimicked 'common' inefficient off-gassing ascents and sub-clinical DCS (excessive micro bubbles) profiles.
Other things that make me feel decisively "less fatigued" after a dive:
1. Proper ascent rate at 9m per min until first stop (see 'best ascent speed').
2. Multiple safety stops at 9, 6 and 3m (e.g. ANDI ascent protocol).
3. Using an ascent gas (i.e. 40-50% O2) to off-gas more efficiently.
4. Proper ascent rate <3m per minute from first stop onwards.
For novice divers, in short, you shouldn't feel fatigued after scuba diving. If you do.... or if you notice nitrox 'reducing fatigue', then also consider analyzing and refining your ascent practices....