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Rising Obesity in Children Prompts Call to Action
On Thu, 28 Aug 2003 07:33:49 -0700, "D. C. Sessions"
wrote: In , Tsu Dho Nimh wrote: Adult formula: BMI = ( Weight in Pounds /(Height in inches squared) x 703 This implies that for constant BMI, you get proportionately skinnier as you get taller. That's a good formula for joint health, but constant proportion would be height cubed. Actually, that would be based on the assumption that as one gets taller, one should also get wider, which isn't necessarily true. And a more appropriate rough approximation of the humanoid shape is a cylinder, not a cube. In that case, there is height L and radius R, so that body mass is proportional to (L*R^2)/2, instead of a cube of length X where body mass is proportional to X^3. In other words, there is not just one variable with an exponent of 3. Even taking this further, biological scaling is rather complex and does not typically follow simple Euclidean geometry anyway. For example, many physiologic functions scale to the 3/4 power of body mass across the spectrum of living things. PF |
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Rising Obesity in Children Prompts Call to Action
In , PF Riley wrote:
Actually, that would be based on the assumption that as one gets taller, one should also get wider, which isn't necessarily true. And a more appropriate rough approximation of the humanoid shape is a cylinder, not a cube. In that case, there is height L and radius R, so that body mass is proportional to (L*R^2)/2, instead of a cube of length X where body mass is proportional to X^3. In other words, there is not just one variable with an exponent of 3. Shape doesn't matter as long as the proportions don't change. Even taking this further, biological scaling is rather complex and does not typically follow simple Euclidean geometry anyway. For example, many physiologic functions scale to the 3/4 power of body mass across the spectrum of living things. Yup -- that's thermodynamics. Because of the need to get rid of heat, metabolic functions go up with surface area (x**2) instead of mass (x**3) so that even with constant proportion, you get (m**0.67). Add the fact that hydrostatic pressure drives added mass towards horizontal rather than vertical growth, and the mechanics of joint strength [1] drives bone and joint size to go up faster than height. The net result is that an optimized body tends towards a mass of greater than h**3. [1] Joint load (second moment) goes up at about h**4, while joint strength goes up at most as r**3, so joints get wider somewhat faster than limbs get longer. -- | Microsoft: "A reputation for releasing inferior software will make | | it more difficult for a software vendor to induce customers to pay | | for new products or new versions of existing products." | end |
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Rising Obesity in Children Prompts Call to Action
microsoft children
micro activities making soft kids. PF Riley wrote in message ... On Thu, 28 Aug 2003 07:33:49 -0700, "D. C. Sessions" wrote: In , Tsu Dho Nimh wrote: Adult formula: BMI = ( Weight in Pounds /(Height in inches squared) x 703 This implies that for constant BMI, you get proportionately skinnier as you get taller. That's a good formula for joint health, but constant proportion would be height cubed. Actually, that would be based on the assumption that as one gets taller, one should also get wider, which isn't necessarily true. And a more appropriate rough approximation of the humanoid shape is a cylinder, not a cube. In that case, there is height L and radius R, so that body mass is proportional to (L*R^2)/2, instead of a cube of length X where body mass is proportional to X^3. In other words, there is not just one variable with an exponent of 3. Even taking this further, biological scaling is rather complex and does not typically follow simple Euclidean geometry anyway. For example, many physiologic functions scale to the 3/4 power of body mass across the spectrum of living things. PF |
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