So, there's a company that comes 'round to the gym at my place of employment every few months and does hydrostatic body fat testing. I've never bothered to get my body fat percentage measured before, but now that I'm lifting weights, I figured I should get a baseline on my lean body mass, just so I can see if I actually manage to put on any muscle.
The test is fairly simple. You put on a bathing suit, and they weigh you. They measure your ankle circumference to get a read on whether you are small, medium, or large-boned. (I'm solidly medium.)Then you get into a tank of water in a sort of push-up position, with your hands and feet balanced on a metal frame. You lower yourself into the water and blow all the air out of your lungs, and they weigh you in the water. You do this about 3 or 4 times - it takes a bit of practice to get yourself fully submerged and get all the air out of your lungs. By the time you've toweled off and changed back into your clothes, they've crunched the numbers.
I'd guessed that my body fat percentage would be in the low thirties, and I wasn't far off. The relevant numbers: Body Fat %: 34.29% (Average is 33%. The recommended target for a woman my age is 22% to 28%.) Fat Body Mass: 57.69 lbs. Lean Body Mass: 110.56 lbs. (This is apparently exactly what it should be for a 5' 3" woman of medium build. That's nice to know - I've been a bit worried that with the weight fluctuations I went through in my late twenties and early thirties that I might have ended up a bit under-muscled.)
So, there's my baseline. I suppose I'll get retested in 6 months or a year and see if I've managed to move any of those numbers in interesting directions.