14 January 2012
Because I sort of feel that karma requires me to participate in other people's studies so that people will participate in mine, I recently signed up for a study of physical activity in older women, older being defined as 50+. It's part of an Oz breast cancer study looking at risk factors and this one is specifically trying to determine which of 3 electronic activity monitoring devices is best for recording physical activity. I enrolled in mid-January and was selected for the two-week full-on sub-sample.
At the enrollment visit, I had my height, weight and body fat % measured and drank a small amount of isotope-labeled water. The degradation of the isotope over time is the standard against which the output of the monitors is compared. Every day I peed in a cup, and plotting the declining quantity of the isotope in each day's sample generated a curve that described my metabolic rate. I also kept a daily diary of activity.
The monitors were: 1) an accelerometer in a small red plastic case, attached to a black elastic waistband, that sits on my right hip (photo on right); 2) a grey armband with a small plastic device that records galvanic skin response, i.e. sweating, Velcro'd on my right upper arm (also on right); and 3) the most recognisably medical thingie, a double-ended black affair with two electrode attachments, one to monitor my ECG and the other another accelerometer (in situ, photo left). I was allowed to remove #s 1 and 2 for showering, swimming and sleeping. #3 stayed on all the time except once in the middle of the week I had to change the electrodes. This was accomplished by peeling the old ones off, washing the spots, roughing up the skin a bit with emery paper, then wiping with alcohol (ouch! that stung!) for optimal adherence and then reapplying new ones.
So how were these monitors? #1 overall wasn't bad. It was comfortable to wear, and relatively nonintrusive. Its worst characteristic was probably the excess elastic that hung down in the front from my waist. When I went back for my mid-trial visit, the research assistant gave me a clip for it and that was much better. #2 was a bit more confronting as I noticed it when I moved my arm, and it created a muffin top of arm fat/skin above it that wasn't that nice to look at. On the plus side, it played a happy little electronic tune every time I took it off or put it on again. #3 was the secret monitor, not visible externally at all unless I were to wear a bikini (and that didn't happen so no worries there). Its downside was a slight degree of skin irritation, ranging from barely noticeable to somewhat obnoxious, just from it being there all the time.
At mid-trial I brought in my week's worth of pee samples and my activity log and the research assistant downloaded information from the 3 monitors, gave them back to me with another 7 specimen cups and a new activity log and sent me off for the final week. Oh, and I got results of the body fat % testing. 28.3%. When the data were all in, I got results from analysis of the falling isotope levels, which confirmed my suspicion that my postmenopausal metabolic rate is somewhere in the snail range.
Hooray for science!