Undercurrent--"Why Divers Die"

[ams511]

Mike I think what he is alluding to is the risk per dive. It is hard to follow his math/logic, but we need to make allowances because English is not his native language.

He does have a point about the other factors, in economics they are called correlated omitted variables. It could be that the obese divers are older, we all tend to put on weight as we age. It could also be that their skills are rusty having been certified when they were young and fit. I am suspect of any study that finds a simple correlation between factors and then tried to weave a story around it. I know some pretty hefty divers that are better than me, after all underwater we are all weightless.

 

[Cacia]

correlated omitted variables.

and the sheer fact that they have become "divers" has selected for certain variables.

 

[ams511]

and the sheer fact that they have become "divers" has selected for certain variables.

That is self-selection bias, however being we are comparing accidents within the recreational diving group it shouldn't be much of a problem.

 

[captain]

From the back of my 1970 YMCA card
If I recall this was done on the first day of class.

Tread water, feet only, no hands for 3 minutes
Swim 300 yards with out stopping.
Tow an inert swimmer 40 yards
Float motionless 15 minutes ( survival float accepted in case of negative bouyancy)
Swim 50 feet underwater without a push off

 

[boulderjohn]

Dan published a couple of articles on obesity in Alert Diver a few years ago, using their BMI statistics. I wrote a letter to the editor challenging those statistics, and I was subsequently contacted by the editor. We had an interesting exchange for a while. She told me that since my letter had arrived, they had done some research on BMI and decided that there were some problems with it. She specifically cited an event in Arkansas (I believe) in which a school district went into an uproar because the BMI indicated a terrible percentage of their children were obese. After an investigation, they decided that the BMI was ridiculously off base as a determining factor for fitness. She asked me if I was interested in writing an article on this topic, but I begged off as not having enough time and not being qualified enough. She got a doctor to write an article, and they printed it along with my letter. He concluded that the BMI was just about the worst indicator of fitness available to you. That was a couple of years ago.

What spurred me was this. At about that time, I had a hydrostatic body fat measurement, the most accurate system for measuring body fat there is. It measured me at 19% (I think). Now, that's not too bad, but according to the BMI, I was nearly obese. The printout I got with my body fat test estimated my body fat percentage if I lost weight through fat loss only. According to those figures, I would reach the fitness level for BMI only if I had a body fat percentage of 0%! The only way I can realistically reach the BMI fitness level for my height is through atrophy--I have to lose a lot of muscle mass.

An earlier poster mentioned NFL linemen. It is not just lineman--more than 90% of the NFL is obese. Ladainian Tomlinson is obese. Tatum Bell, the small, sprinting running back for the Broncos, is obese, according to the BMI.

If you are into fitness in a way that includes resistance training, you will almost certainly be officially overweight according to the BMI.

 

[Jon C]

He does have a point about the other factors, in economics they are called correlated omitted variables.

My mom always told me to eat my correlated omitted variables or I would get no dessert. Never knew what she was talking about until now!

 

[Charlie59]

Do you dare compare a muscular athlete to a 40 year old with a 40 inch waist line? I would think that people on this board would be aware if their BMI is increased due to exceptional muscle mass versus obesity (I mean, be real). If you don't like the BMI of 30, look at yourself if it is >35 or 40.

No one is trying to set up guidelines on diving based on BMI, but you may want to examine your overall physical state if it is increased. No one has "big bones".

 

[Cacia]

cited an event in Arkansas (I believe) in which a school district went into an uproar because the BMI indicated a terrible percentage of their children were obese.

and they don't have obese kids, right? I lived in Arkansas once. This reminds me of re-writing the science when you don't like the results.

but I get your point.

He concluded that the BMI was just about the worst indicator of fitness available to you.

You know, I know what BMI is...and all along I have been thinking ...the body fat percentage, done with the calipers. my bad. yes, BMI is pretty obsolete as anything but a very rough guide. I have been arguing body fat percentage...easy to measure.

Still, BMI for kids would be based on average weights/hts. Not too many kids are body builders.

 

[boulderjohn]

Still, BMI for kids would be based on average weights/hts. Not too many kids are body builders.

Everyone has always siad tht the BMI is not accurate for bodybuilders. The point is that it is not just bodybuilders who are affected. The BMI is inaccurate for anyone who does regular exercise involving any kind of resistance training.

 

[Charlie59]

Sure, that's right, that's why NIH and CDC use it in population evaluation. The government loves to throw away your money.

I see alot of folks with "BMI issues" and I can tell you it is a small minority that has these issues due to resistance training (more like lack of resistance training).