Hydrostatic Weighing

One of the things I am keying on in my preparation for Ironman is 'body composition', or to put it more simply, body fat percentage. I want to have more muscle carrying around less fat, that just makes sense. I will be faster and able to go longer with that greater efficiency. I also know its healthier and more attreactive to have a flat stomach!

In early December I set some benchmark measurements, including this dubious online calculation of Body Fat Percent:

My weight is now 220 pounds, up 10 pounds since early October. I measured by body fat percentage last night using an online calculator. The tool uses weight, age and some body dimensions to estimate percent fat. I scored 26.6% (fat). Not sure how accurate the percent is, but the component measurements were as follows: waist (belly) 45 hips 43 forearm 12 wrist 7.5

Last night I remeasured and got

waist (belly) 45
hips 41
forearm 12.5
wrist 7

24.8%

The acuracy of this type of circumfrence test is dubious. Some basic assumptions are made, not the least of which is the accuracy of the measurements in each test, and compared between tests. The difference between these two tests is 1.8%. This could be real prgress, or a difference in the tightness of the measuring tape. That said, I do believe its helpful to periodically measure my waist along with stepping on the scale to guage my progress.

This morning I made my way over to Adelphi University and the Human Performance Program labs for actual hydrostatic weighing, the second most accurate means of measuring body composition. (The most accurate method is cadaver analysis, probably the least popular method). Hydrostatic weighing involves measurement of body density and the application of a mathematical formula to estimate fat mass, and thus the percent of fat compared to the total body mass.

I met one of the two grad students who would conduct the test, in the lobby of the new Phys Ed complex. She walked me down to the locker room, told me to change and meet her in the lab, behind the bleachers at the far end of the basketball courts.

Awesome Human Perfomace grad students
Courtney and Sarah administerd my test

I had my VO2 max testing done here two years ago, in Woodruff Hall, next door. That building is under renovation, and until that's done, the Human Performance lab is in the equipment closet! It's clean and orderly, but yeah, mats and cones and so forth in there. Off to the side there's the tank, a Detecto scale and a couple of computers.

The Tank

First they weighed me, wearing only my swim suit. Next they measured my lung capacity, by plugging my nose, having me take a huge breath, clamp my mouth around this hair drier looking thing and blow out as much as i could. My "vital capacity" was 4810 ml. I believe this must be used to calculate the volume of my body without air in my lungs.

Now I climbed into the tank. It was hot! 34 C or 93 F!!! The tank has a swing hanging in the middle, which is attached to the scale. I hung out in there to get rid of any air bubbles in my suit, dunked my head to get the air out of my hair, fill up my ears.


Next I needed to expel all the air from my lungs, remain completely underwater and not touch the swing seat, so they could get the tare weight (weight of the scale without me on it).


Now the hard part. I put a weighted belt around my waist (this belt was on the seat when measuring tare weight), sat on the swing, exhaled as much as i could and stayed under the water without touching anything inside the tank except the scale. Sarah watched me to see when my bubble stopped, and Courtney watched the monitor which lit up when the swing was completely still. There is a learning curve involved with this, and you don't realize how hard this is, to get all thew air out of your lungs and then hold it, without moving.



We did probably 10 or 12 trys at this to get 10 good results, and ended up averaging the two best readings of the ones we kept. The ladies did their calculations and determined the following:

Weight 217 lbs
% Body Fat 31%
Estimated fat Mass 67.27 lbs
Estimated Fat Free Mass 149.73 lbs
Target Weight at 10% Body Fat 166 lbs.

This 31% number is higher than I expected, based on the online tests and what i have read is 'average'. So I am glad I did this, it really does give me a good benchmark to work from, and a little kick in the ass as well, to shed some of this bodyfat. i think I can still use the online calculator on an interim basis to see where I am at.

On the other hand, this suggestion that my ideal race weight should be 166 lbs...quite frankly i do not see how that coudl be right. Thats 51 pounds ligher than I am today. Ok, maybe over time I could get there, but just imaginign that change between now and July, you'd have to consider checkign me into a clinic for eating disorders. I would be emaciated, a concentraion camp survivor.

That calculation assumes my lean body mass remains static. In other words, lose fat, do not gain muslce. Is there maybe another way to view this? What if I maintain my fat body mass and increase the lean part? With that sssumption, I simply need to add muscle until I weight 670 pounds. This also assumes that a 10% body fat is desired. Is it?

Ok maybe a different approach. Based on those charts you see in the doctors office, for my height I should weigh between 174 and 188, assuming a 'large frame'. So couldnt we just say that instead of being overweight, i am just under height. If I could get up to 7 feet tall I'd be perfect.

On the way back to the office, I stopped at the deli for a ham and swiss in rye. Enjoyed it. Last time I will do that for a whiel I guess. As much as I hate the idea of it, tommorow I start counting calories.