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All the Perl that's Practical to Extract and Report

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  • Keep in mind that if you're biking often (especially up and down hills) there's a good chance you're building leg muscle. That means you could be losing fat without losing weight.

    A body fat measurement is in order I think. Then, another one every 3 months or so.

    • I got ahold of a scale that purports to measure body fat percentage electrically. Its reliability is horrendous, however. It varies extremely based on the moistness of the bottom of my feet, in addition to other factors I can't fathom. I figure it's better than nothing, though, and I track and trend my body fat percentage daily with the same calculations I use for body weight (from the Hacker's Diet). I figure eventually it would be nice to get a real measurement done, with caliper or even better, with

      J. David works really hard, has a passion for writing good software, and knows many of the world's best Perl programmers
      • by phillup (4419) on 2004.06.21 17:29 (#31740) Homepage Journal
        I've got one.

        I was also a metrologist [] for 13 years... take that for what it is worth. Throw in a few bucks and you can buy a cup of coffee somewhere...

        Anyway, you are right about the variation. But, from a measurement standpoint, that is to be expected. (Consider, the thing shoots an electric current from one leg to another. The current has to pass thru (and along... there are multiple paths) one leg, the core of your body, and down the other leg. Anything that changes the current flow will change the reading.)

        You should make sure your feet and the unit are dry. Then, use it three times in a row... if it doesn't give you the same reading, plus or minus one digit... I'd suggest not using it. It has to be repeatable over the short run before you can expect it to be repeatable from day to day.

        I'd suspect low battery levels if it deviates between two consecutive readings a few seconds apart.

        The next issue is going to be just like weighing yourself... you have to be consistent about the time of day, etc.

        I have found that my most meaningful data comes if I use the same routine. Get up in the morning, strip, take care of my "daily ritual" (toilet), and weigh immediately (after washing my hands).

        Don't even drink any water before-hand... too much of a variation. Remember, the current is passing thru your body core. I use the bathroom first because I can't "standardize" how much I'm "holding" from the previous day... so emptying out before hand is as close as I can come to being the same from day to day.

        I can take that data, and using just that data... show you where I've taken long walks/runs/bike rides. And... you can see when the "super compensation" of carbohydrate replenishment is done. For me, the deviations line up very well with my activity levels and has been quite repeatable in this regard.

        But, you have to be a real stickler about making sure all of your data is taken under the same conditions if you want to make sense of the variations.

        It gets worse. By noting that the data is shifting with the state of carbohydrate balance in the legs (depleted vs. super-compensated) we come to realize that the device is not intended for use under those circumstances. (In other words... it is not accurate under these conditions.) Instead, it is intended for use by a "normal" person whose body is in its "natural" state.

        (Never mind the irony of such a person not caring about the data this device provices.)

        So, if you want an "accurate" reading of actual body fat. You will need to wait 3 - 7 days for your body to fully recover from your rides and "stabilize"... so that you minimize the effect on the device due to carbohydrate balance in the muscle.

        It also assumes that you do not deviate too far from the normal populace in body structure. So, if you are extremely fat or fit... it will be less accurate for you.

        All in all... I think it is good for trending information, but I wouldn't get too hung up on the actual numbers.

        • You should make sure your feet and the unit are dry.

          Actually the instructions for this unit say your feet should be somewhat moist. That's kind of annoying, as "somewhat" moist is nowhere near precise. I usually don't worry much about it, but I usually weigh right after my morning shower, so my feet are in some varying stage between dry and sopping.

          You're right, you can't get too hung up on the numbers. I keep the info, but if I ever got really serious about it, I'd have to find a more accurate met

          J. David works really hard, has a passion for writing good software, and knows many of the world's best Perl programmers