ajgraz
Lieutenant Commander
- Joined
- Mar 1, 2010
- Messages
- 1,858
Re: Life vest questions
You've given us data for your buddy and for you.
Hydrostatic weighing can give a body density measurement as follows:
Dbody/Dwater = Wbody/(Wbody-Wimmersedbody)
or
Dbody = Dwater*Wbody/(Wbody-Wimmersedbody)
Assuming we're talking about fresh water in your immersion pool, Dwater is 1g/cc. Since the Wbody and Wimmersedbody units will cancel, it doesn't matter if they are in lbs, kgs, or stones.
So let's plug in some numbers:
Dbodybuddy = 1g/cc*(165lb/(165lb-19lb)) = 1.13g/cc
Dbodyyou = 1g/cc*(325lb/(325lb-216lb)) = 2.98g/cc
Lean body tissue has a density around 1.1 g/cc; so your buddy's number passes the sniff test so far, but yours does not. Not even close.
Now, plugging those body density figures into Brozek and Siri formulae for determining body fat percentage (models have a +/-10% accuracy):
http://en.wikipedia.org/wiki/Body_fat_percentage
Brozek formula: BF = (4.57/ρ − 4.142) ? 100
Siri formula is: BF = (4.95/ρ − 4.50) ? 100
Your buddy has a body fat percentage somewhere between -10% and -12%. Ok, there's +/-10% error in the model, your buddy may be extremely lean, I'm wondering if he had a lungful of air, and if you subtracted the weight of the sling in the immersed weighing, etc., etc. In any case, this is somewhere near the bleeding edge of potential reasonableness, and it looks like he's gonna live if strapped to a life jacket.
According to these formulae, you have a body fat percentage of somewhere between -260% and -280%. No friggin' way.
So unless you had 5 bowling balls for breakfast that morning, or your bones are made of depleted uranium, or you have a prosthetic limb made of lead, or you are an android, or your immersion pool was filled with something far less dense than water, or you're off by a decimal place, your numbers are simply impossible.
If your numbers are correct, call Stan Lee and get on that Superhumans show. And strap an 8-man liferaft to your back because that's the only thing gonna save you.
You've given us data for your buddy and for you.
Hydrostatic weighing can give a body density measurement as follows:
Dbody/Dwater = Wbody/(Wbody-Wimmersedbody)
or
Dbody = Dwater*Wbody/(Wbody-Wimmersedbody)
Assuming we're talking about fresh water in your immersion pool, Dwater is 1g/cc. Since the Wbody and Wimmersedbody units will cancel, it doesn't matter if they are in lbs, kgs, or stones.
So let's plug in some numbers:
Dbodybuddy = 1g/cc*(165lb/(165lb-19lb)) = 1.13g/cc
Dbodyyou = 1g/cc*(325lb/(325lb-216lb)) = 2.98g/cc
Lean body tissue has a density around 1.1 g/cc; so your buddy's number passes the sniff test so far, but yours does not. Not even close.
Now, plugging those body density figures into Brozek and Siri formulae for determining body fat percentage (models have a +/-10% accuracy):
http://en.wikipedia.org/wiki/Body_fat_percentage
Brozek formula: BF = (4.57/ρ − 4.142) ? 100
Siri formula is: BF = (4.95/ρ − 4.50) ? 100
Your buddy has a body fat percentage somewhere between -10% and -12%. Ok, there's +/-10% error in the model, your buddy may be extremely lean, I'm wondering if he had a lungful of air, and if you subtracted the weight of the sling in the immersed weighing, etc., etc. In any case, this is somewhere near the bleeding edge of potential reasonableness, and it looks like he's gonna live if strapped to a life jacket.
According to these formulae, you have a body fat percentage of somewhere between -260% and -280%. No friggin' way.
So unless you had 5 bowling balls for breakfast that morning, or your bones are made of depleted uranium, or you have a prosthetic limb made of lead, or you are an android, or your immersion pool was filled with something far less dense than water, or you're off by a decimal place, your numbers are simply impossible.
If your numbers are correct, call Stan Lee and get on that Superhumans show. And strap an 8-man liferaft to your back because that's the only thing gonna save you.