Thursday, June 9, 2011

Ready To Race? Checking Your Body Fat Percentage

Teammates – I thought some of you might be interested in this. In preparation for the major races coming up at the end of the season, I wanted to put a real number on my percentage of body fat - power-to-weight ratio being so important for our typically hilly road races. I thought I would have to head over to San Jose and pay a lot for this so I’ve never done it. Silly me.

It turns out that Dominican Hospital’s Center for Lifestyle Management right over on 610 Frederick Street in Santa Cruz does it and it only costs $79 (total, no tax). You call 831-457-7077 and make an appointment. Eric Hand was the physical therapist who did mine (his sport is beach volleyball). It took about an hour. First he weighed me and took my height. Then he did a skin-fold caliper test and then weighed me in the water tank.

The underwater weighing was interesting (the photo gives you the idea, but that's some other facility, not Dominican's; should have brought my camera). 

You sit in a hanging chair submerged in the water tank. The chair is hooked to a scale overhead and you bend over and dunk your head and shoulders so you’re entirely under water. Then you have to exhale completely to get a true weight. That’s not easy, so they weigh you over and over. We did mine 4 times after which I felt like I’d done 100 sit-ups.

Once the weighing was done Eric crunched the numbers on his computer, went over the results with me and gave me a nice printout with my target body fat and weight for optimum racing performance. With this number I can finally stop worrying if I’m too fat or too thin (I’m not telling) and train with the right number as my target. Hope you find this information useful,

Jim Langley



Ken said...

Do you know how the amount of air left in your in your lungs was determined (estimated)when you were submerged?

Jim Langley said...

I don't know, Ken. He weighed me 4 times and said that we would keep doing it until he saw consistent numbers. The interesting thing to me was that the skin-fold caliper test and the water weight test resulted in about the same number. If I do it again next year I'll ask him about it.

Dennis the Mennis said...

Yes, I have also had water-tank and skin-fold tests over the years and they are indeed pretty much identical. I wouldn't hesitate to recommend just skin-fold testing, but it's also nice to have the water-tank test done at least once for comparison.

Eddy Price said...

Under water weighing depends upon exhaling as much air as possible from your lungs so all tht's left is the residual lung volume.

Residual lung volume is easily calculated by knowing your height. It is approximately 150 ml of air.