Dan

Again my question or debate is not about the changes in V02 max if you
gain body weight or lose weight. The point I was making is that it is
possible a guy can be quite large and still have a high V02 max. Of
course if that person loses or gains weight there will be a VO2 max
change. We agree on changes with changes in body weight, that is a fact
of life. Also though exercise influences VO2 max. Where we disagree is
that you cannot make an absobulute statement that a large person cannot
have a high VO2 max. There is too much variation in individual
physiology and individual muscle etc. You yourself have stated Terry
weighs almost 300 pounds, and I think you indicated he has a rather high
VO2 max. Yes i realize he is Muscle. But some big fat guys have large
muscles also.  

My point is even with a given VO2 max knowing how to breath is equally
as important for good gas exchange. This is a subject I teach (correct
breathing techniques) I know what it can do to performance and
endurance. I also know that if you have a good VO2 max and breathes
correctly (most people with good VO2 max do breath correct but not all)
that they are amoung the most efficient of atheletes. However with
improper breathing technique a good VO2 maxz under stress loading is
wasted. 

You most look at and develop all the essentials parts of breathing to
get max results. Then you must develop the ability to breath correctly
under a stressful situtation. 

Where `extreme fat does really become a problem is when it compresses
the diaghram and makes correct breathing an impossibility and at some
point that will happen if a person has enough midriff fat.
 
Now on DCS yes cross section/densisty of thetissue (s) will predispose
someone in my opnion to DCS, Personally I think there is a direct
comparision to probability of DCS and degree of fat, not to the
magnitude that you presented. The purpose in me putting Phelps work out
was to illustrate that danger of fat and DCS I think that was a rather
strong point to most people who would read that. Yet there is a lot of
recently published material that refutes this. I do not agree but it is
not up to me to make the decision on DCS probability. 

You need to talk to people who I have trained and see the emphasis that
I place on fitness both physcial and mental in my courses. We do
breathing exercises we discuss fitness. All the new IANTD workbooks are
heavy into this but I would never state an absobulute about a individual
unless I knew their training programs. I learned a long time ago to not
judge the book by its cover. 

I als do not like to mandate that everyone I know has to adopt my
beleifs, I advocate everything should be done a a risk benefit
evaluation then people can determine why they should or should not do
someting. This ranges fro fitness to diving to equipment config what
ever. People need to list the why of what they do or should do and the
risk of what they do and how to miminize that risk.

Concerning diving the first hing is accept I can dive doing this or I
can get hurt very bad by DCS etc. Now what can I do to reduce the risk.
I think this concept will motivate more people to make intelligent
decisions about what to do than juswt ramming it down there throat. and
if someone choses not to do a corrective action then at least they have
become aware of the risk. This is my concept opn education.

We have a new text being published the chapter I wrote on physiology is
full of the benefits of exercise, diet, VO2 max and the advantageds of
these factors and the risk of being overweight. You will love the
chapter. But there are no absobulutes in regard to size of a person on
an indivdual bases.That is and has been my big point. 

I guess we have let this get out of hand a little as we seem to have
offended some people. I did not mean to do so. I do not think not being
in shape or being in shape and overweight makes a person better or
worse. Some of my best friends are way overweight I still like them and
respect them. I do think they should do a risk benefit profile for the
type dives they do. My son for instance has made the decision not to do
serious dives until he drops somew weoght. He has alot of musclke
underneath his bodyweight but he realizes theextra weight makes him more
at risk in deep dives so he is avoiding them until he drops weight.He
did this decision based on his personal assement of the risk, not on my
stands.

You mentioned Bill Rennaker, that would be interesting I think he would
do the testing and be excited about it. I would like to see the results
as he is in a category of many divers. Overweight but very active
diving. I think a VO2 max. a check on breathing technique and a tradmill
stress test would be great.

I have a good friend Dudley Crossman who does research in diving and
exertion. In fact he has done a lot of work putting divers on exercise
bikes both in chamber and in water and measuring the results usually in
regard to equipment delivery. the last time I worked with him he had us
on a rebreather (UT 240 shudder) exercising in ten feet of water
breathing on the unit(in this capacity the unit did ok) at 50 watt
seconds for 20 minutes then 100 watts for 40 minutes (some of the guys
could not maintain the 40 minutes at 100 watts so for them they did 20
minutes sets/cycles)and then a couple of us (Billy Deands myself Mike
Fowler at 150 watts for 20 minutes. You can get a lot of equipment and
fitness data on this type of testing. You see the co2 retainers to.
Fprgot my son evenas big as he is was one of the few of us who could do
both the  20 min at 50 watts then stepped up to 40 minutes at 100 then
stepped up to 20 min at 150 watts drill start to finsh with out a break.

This is some of the testig i would like to have us do also. We were
doing it to evaluate the unit and its delivery capacity but it also
evaluates the fitness level of the diver. EDU has also done a lot of
work along these lines.

I realize rat and human physiology is vastly diferent but I thought it
was a rather interesting experiment on the effects of fat and DCS onrats
and that there is some parallel inhow exceptional fat would effect DCS. 

I thought the point was clear that the rats even with a more efficient
physiology than ours were getting bent more and more seriously as the
body weight was increased. Note the death rate in the really obese rats. 
Dan Volker wrote:
> 
> The rat test.
> 
> One of my sources for my views on VO2 max and fitness, is the Exercise
> Physiologist for the U.S. Speedskating team, Carl Foster.
> 
> In Carl's discussion of VO2 max, he places the average , untrained aerobic
> system of a human at around 35 to 40 ml/kg of body weight ( the average
> weight human). Elite cyclists and swimmers may be in the low 60's to 70's.
> The world's best scores, by sport, belong to Nordic skiers (Cross Country
> skiers), who have scored as high as 90 ml/kg.   Carl says,, in perspective,
> the family Beagle ( a small dog ) has a VO2 max of around 135, without any
> special training at all.  The volume or body mass of the subject being
> tested is critical here, in that it has major effects on gas exchange
> rates-----as Bill Mee likes to say, its about cross sectional area, and
> perfusion within a huge area, compared to a small cross sectional
> area----the very fat person has such poor vascularization within their much
> larger mass, that it will take much longer to expose the far reaches of it
> to the new gradient each deco stop represents. This, in addition to the
> problem of the much larger body of the very obese, that their heart will
> require much more time to circulate the entire body volume of blood through
> the lungs.
> 
> The rat is a poor model for deco predictions in humans, since its tiny cross
> sectional area, even in the most obese of rats, is still much smaller than
> that of a human, and we would expect even the fattest rodent ( the Brett
> Gilliam rodent ??) would still have a much higher VO2 max than any human
> which ever existed-----with such fast gas exchange, we would not expect to
> see a DCS test with lean rats and fat rats, in any way mimic human DCS
> conditions. However, the "Gilliam Rodents" may set new world records on Deep
> Air!!! :)
> If you want to use lab animals for a trimix deco model, we will need to more
> closely approximate human cross sectional area, mass, and  gas exchange
> potential....
> George told me that Bill Renaker looks a great deal like a large Pig---maybe
> this should be the test animal :)
> 
> Regards,
> Dan Volker
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