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Thread: mets to watts?

  1. #1
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    mets to watts?

    So I'm at the gym on an elliptical or a stationary bike and one of the LEDs tells me I'm putting out, say, 14 mets. What is a "met"? Is there a formula to convert to watts. Why doesn't gym equipment ever have a watt readout?

  2. #2
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    Doesn't look like you can convert mets -> watts

    http://findarticles.com/p/articles/m...23/ai_n6004469

    Q In addition to calories burned, time and distance, the cardio machines at my gym give readouts for METs and watts. What are these measurements, and should I pay attention to them?

    A "These are ways to measure the amount of work you are doing, but for the average person, they're not very practical," says Dixie Stanforth, M.S., a lecturer in the kinesiology department at the University of Texas at Austin.

    A MET is defined as a "multiple of the resting metabolic rate." One MET equals the amount of oxygen your body takes in when you're not moving. "MET values tell you how much harder you're working when compared with rest," Stanforth says. "So exercise performed at three METs requires three times the amount of oxygen consumed at rest."

    A watt is a measure of power, equal to force multiplied by distance divided by time. "You generally see watts on rowing machines or bikes," Stanforth says. "Basically, this is a way of looking at how much power you are generating. For an athlete, this can be meaningful. You can see how much power you're generating in a given gear on your bike, for example. But for most people, it's overkill."

    Rather than focus on METs or watts, focus on distance, time and intensity level. Many cardio machines have built-in heart-rate monitors, which can help you track your progress as well. If, say, you can exercise at level 7 on the elliptical trainer for 20 minutes at a certain heart rate and two months later you can work out for the same time at the same level at a lower heart rate, then you know you have become more fit. (You also can judge your progress by what is known as your RPE, or your rate of perceived exertion; that is, you're making progress when a workout feels easier.)

  3. #3
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    Poor correlation

    Quote Originally Posted by mendo
    So I'm at the gym on an elliptical or a stationary bike and one of the LEDs tells me I'm putting out, say, 14 mets. What is a "met"? Is there a formula to convert to watts. Why doesn't gym equipment ever have a watt readout?
    It appears that METs are a poor way to judge effort. Bicycling magazine uses some table or another of METs and bicycling to calculate the calories burned (directly connected to watts produced) for a given bike ride, and the numbers are laughingly high. Bicycling often quotes numbers around 40 calories per mile at 15 mph, when in fact the wattage/calories is roughly half that. I suspect that METs is just a marketing gimmick from the equipment manufacturer. After all, why report something useful and precise, like watts, when you can baffle your customer into thinking they're getting more exercise than they actually are.

    BTW, there is a fitness/training forum on this site, and that is a better place to post this sort of question.

  4. #4
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    http://en.wikipedia.org/wiki/Metabolic_equivalent
    They give a MET as 1 kcal / kg / hr

    It basically the rate of work done by your body, normalized by your weight.
    For example, if you perform 14 MET's and weigh 160 lbs (72.6 kg), you burn:
    14 kcal / kg / hr * 72.6 kg = 1016 kcal / hr
    This is the rate of calories burned.

    Assuming a 24% efficiency (only 24% goes into the bike, I've seen this used many places, including here: http://www.braydenwm.com/calburn.htm
    1016 *0.24 = 254.0117 kcal/hr put into the drive train

    Convert kcal/hr to Watts to get an estimate of your power:
    254.0117 kcal/hr * 4186.795 J/kcal / 3600 sec /hr = 284.6 (J/s or Watts).

  5. #5
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    METs and VO2

    1 MET = 3.5 mililiters of oxygen per kilogram of body weight. If an elliptical trainer reads "14 METs", in theory you would be working at a level equal to 49 VO2. If you were maxed out, then your theoretical VO2 max on an ellipitcial trainer would be 49 (Lance Armstrong topped out at 84). The problem is the elltipical trainer is probably very inaccurate. 14 METs is a sizable effort. Most people would be very hard pressed to exceed 15-16 METs. In fact, 16 METs is grossly accurate to running at 10 mph (6:00 minute mile). And as far as I know, a MET equals a MET equals a MET. VO2 differs mainly because the bodyweight measurement.

    Converting watts to METs is evidently not high on the exercise physiologoist training agenda. It seems cycling and rowing are measured in watts and running is measured in METs. Swimming and X-C skiing, I don't how they measure out.

  6. #6
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    Smile This is from a nerd

    1 met = 0.527427128 W/lb

    This is useful.

  7. #7
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    Phew !! What a relief. For a minute there I thought the Amazin's were relocating to South L.A.

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