You guys are ridiculous, stop it!
[quote]LiveFromThe781 wrote:
Because we dont want to do a god damned equation to figure out whether someone is big or not!
/thread
[/quote]
Fixed
[quote]waylanderxx wrote:
You guys are ridiculous, stop it![/quote]
Tough crowd! Sure, how you look is what counts, not whether you hit some magic number or formula. It’s just interesting to me. Not to everyone, obviously. 
I understand what you’re saying, that height to weight is better than weight alone. If one could take BMI and then factor in waistline , then yes, it could be helpful. BMI in itself has no intrinsic ability to differentiate muscle from lard, but if you’re 6 foot, 200+ lbs with a 30 inch waistline or something, then you either have bizarre fat distribution, or you’re carrying around a lot of muscle.
[quote]MarkT wrote:
wushu_1984 wrote:
PLEASE IGNORE IF NOT A NERD:
Some super nerdage:
3.0lbs per inch gives {Height, BMI}:
{5’4",33}, {5’8",31}, {6’,29.3}, {6’4",27.8}
Average for 13 BMI’s between 5’4 to 6’4" = 30.22
Wushu, I like your rule, especially the thought of aiming for “obesity” as a goal.
Upping the nerdage level a bit (fair warning!)…
I’ve wondered before about the various lbs/inch values people toss around, like 3 lbs per each inch of your height vs. 5-10 lbs per inches of height difference when comparing people. Wushu’s comparison to 3 lbs/in shows his BMI rule is not too different but has some different trend with height.
Specifically, the rules agree for a 5’10" height, where both say 210 lbs is “big”. Wushu’s rule says your weight should scale like height squared to keep the same look, and at 5’10" and 210 lbs, that translates into 6.0 lbs/inch.
On the other hand, a physicist can’t help but say “consider the spherical human”, and define a “Body Sphericity Index”:
BSI = Mass (kg) / (Height (m))^3 or
BSI = 27700 * Weight (lbs) / (Height (inches))^3
If you shrink someone keeping all proportions the same, they’ll have the same BSI. (And if they are spherical, BSI = 524).
If I pick BSI = 17 as the cutoff for “bigness”, this matches Wushu’s rule and the 3 lbs/inch rule for a 5’10" guy. But changes in height translate into 9.0 lbs/inch.
[/quote]
Some quality nerdage here Good to have a scientist (stalked your profile) on the job.
AGAIN - PLEASE IGNORE IF NOT A NERD
There was a paper here:
http://jap.physiology.org/cgi/reprint/89/3/1061.pdf
In here they suggested that muscle mass scaled almost exactly with height cubed (Ht^3.16). So there is some support for your suggestion. Although these were competitive weightlifters as opposed to bodybuilders.
==========================
Nerdage aside.
Even the most straightforward suggestion of BlueCollar’s 3lbs per inch (with abs showing) is so much better than 200lbs.
not to piss on your parade, but BMI is not really comparable across various ethnic groups.
a BMI of 30 (while keeping BF% constant) provides different looks for african americans, caucasians, asians, native americans, etc, etc…
so while a bench mark of 200lbs requires qualifications to be of any value, so does a bmi of 30.
so i guess as stated above look in the mirror
extract:
“Subjects with relatively long legs will have lower BMIs… (for example) the ‘longleggedness’ of the Australian aboriginals contributes to 2 kg/m2 to their low BMI.”
[quote]wushu_1984 wrote:
Based on an assumption that BW/Vol = Constant one can see that BW = Vol * Constant.
quote]
But that, of course, is an assumption that is WRONG. The assumption lies at the heart of why BMI is usless for its intended purpose. Fat people with low muscle mass are less dense than lean muscular people.