out-of-shape divers doing things like diving the doria

[Gerbs]

Human fat does not = marine mammal blubber.


All other things being equal, a fatter person has more surface area, and would lose heat at a higher rate than someone with less surface area. So being fat will make one more vulnerable to hypothermia, not less.

I'm open to being corrected if someone can post valid scientific info to the contrary.

More surface area, yes. However...

Weight goes up as a cube relative to size.
Surface area goes up as a square relative to size.

As you get bigger, you have less surface per volume.

Hence in the arctic conditions, you tend to find a certain minimum size of animal, as the metabolism to keep the heat is just not possible. Also, whales need their tail fin as a heat rejection mechanism, as otherwise they would boil themselves.

Gerbs

 

[halocline]

All other things being equal, a fatter person has more surface area, and would lose heat at a higher rate than someone with less surface area. So being fat will make one more vulnerable to hypothermia, not less.

I'm open to being corrected if someone can post valid scientific info to the contrary.

Larger animals/people have more surface area, but even larger volumes...shape being equal, larger size means lower ratio of surface area to volume. That would be more insulating, not less. And of course, the shape does change; a sphere has the lowest surface area to volume ratio. All other factors equal, round people will be less vulnerable to heat loss through surface conductivity than narrow long people.

There are lots of other factors in hypothermia, though.

 

[humanbeing]

So, here's what I've come away from this thread with:

being in shape for demanding dives = good, sane
being out of shape for demanding dives = bad, crazy

no substantial evidence to offset/challenge this paradigm

 

[Rhone Man]

So, here's what I've come away from this thread with:

being in shape for [-]demanding dives[/-] life = good, sane
being out of shape for [-]demanding dives[/-] anything active = bad, crazy

no substantial evidence to offset/challenge this paradigm

Suggested modification...

 

[vladimir]

So, here's what I've come away from this thread with:

being in shape for demanding dives = good, sane
being out of shape for demanding dives = bad, crazy

no substantial evidence to offset/challenge this paradigm

What did you come into the thread with? Which posts confirmed your view that it was "crazy" to be out of shape for demanding dives? Was your view that a diver's fitness can be reliably judged by looking at a photograph altered at all? Assuming for a moment that we replace "bad" with "suboptimal" and "crazy" with "perhaps reckless" in your conclusion above, would you think that is very insightful, or intuitively obvious?

 

[knowone]

It's quite easy to cook yourself in a drysuit or a wetsuit no matter what your size.
But who's "the guy" with the bmi, that can best handle post dive.

 

[rcolsen]

What is the definition for being in shape? I still have not seen it defined. It would seem that the standard for being fit (in shape) is defined by the activity/sport. Example a 130# marathon runner is in shape to run long distance and a 250# Olympic weight lifter tossing 700#+ is in shape for his sport. Both train are athletes and work towards a goal and stay in shape for what they do. If your medical doctor thinks you are fit to dive. Then dive and enjoy it. Maybe there should be a post on Nitrogen build up in inflated heads.

 

[vladimir]

What is the definition for being in shape? I still have not seen it defined.

Here's one definition, ~40 posts ago in this thread:

DAN recommends a cardiovascular fitness level of 13 METS exercise tolerance, as evidenced by a normal stress EKG test (13 mets or stage 4 of the Bruce protocol ce stress test.

 

[DCBC]

DAN recommends a cardiovascular fitness level of 13 METS exercise tolerance, as evidenced by a normal stress EKG test (13 mets or stage 4 of the Bruce protocol ce stress test.

To put this in perspective, the average person who runs an 8 minute mile is at 12 METS. 13 METS is achieved when the time is usually between 6 & 7 minutes.

Although it's best to have every diver in good condition from a medical perspective, I question if this is a very practical standard. Today scuba is enjoyed by people as young as 10 and as old as 80+. These people seldom have the capability to run a 6 minute mile, nor is this a reasonable expectation imo.

http://www.cardiology.org/recentpapers/QUESTJM.PDF

 

[halocline]

I'm not sure that an 'average' person in the U.S. could run a mile in any amount of time, let alone 8 minutes. 7 minutes/mile is a pretty good pace, even for an athletic regular runner, and 6 is really moving.