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Old 01-24-08, 11:13 AM   #1
bdcheung
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Monod, CP, and Weight

How does weight factor in to calculating estimated CP's? I noticed that as I adjust my race-weight downward, CP60 also goes down (significantly).

/confused
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Old 01-24-08, 11:29 AM   #2
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Me too. One has nothing to do with the other.
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Old 01-24-08, 11:55 AM   #3
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They probably estimate it based on a W/kg ratio, not a straight Watts function.
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Old 01-24-08, 11:59 AM   #4
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lame! My weight goes up and down every time I take a drink or a piss - that doesn't mean my FTP changes.
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Old 01-24-08, 12:13 PM   #5
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I just don't believe that the four pounds I pooped this morning will lower my FTP by 7 watts.
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Old 01-24-08, 12:14 PM   #6
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Originally Posted by bdcheung View Post
lame! My weight goes up and down every time I take a drink or a piss - that doesn't mean my FTP changes.
Right, and that's why this is just an estimate.

Weight is a very tricky thing to nail down - the amount of food or water in your system at any given time fluctuates a lot. Sometimes during my intense training days, my weight will fluctuate +- 7 pounds from my 165 base.

If you measure your weight fairly often, you can see the noise and thus correct for it somewhat.

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Old 01-24-08, 12:33 PM   #7
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I just don't believe that the four pounds I pooped this morning will lower my FTP by 7 watts.
If you actually took a four pound dump this morning, you have more urgent concerns.
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Old 01-24-08, 02:33 PM   #8
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Relative VO2Max changes with weight.
Note the key word "relative." Absolute VO2max does not change with weight.

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Lactate Threshold is some percentage of VO2Max.
It's also some percentage of the distance from the Sun to the Moon. Just because two numbers can be divided does not mean they are directly proportional and move in lock step. LT can easily be moved relative to VO2max, and I believe VO2max can move without a corresponding change in LT.

As to the role of weight. look at the units. FTP and LT are both measured in units of power,, e.g., Watts, weight does not enter into it.[/QUOTE]
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Old 01-24-08, 03:19 PM   #9
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As to the role of weight. look at the units. FTP and LT are both measured in units of power,, e.g., Watts, weight does not enter into it.
Hence my confusion on why the projected CP60 changes (rather drastically) with weight.
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Old 01-24-08, 03:26 PM   #10
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Using MonodCP.xls, I can reduce my weight by 100 lbs and my FTP remains constant. CP also remains constant.

W/kg changes of course.
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Old 01-24-08, 03:29 PM   #11
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Using MonodCP.xls, I can reduce my weight by 100 lbs and my FTP remains constant. CP also remains constant.

W/kg changes of course.
I was using the other spreadsheet - the one where you can enter 4 tested values. I guess that answers the question of which is more reliable.
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Old 01-24-08, 03:53 PM   #12
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Interesting. Yeah, they must be making some assumptions about how much power you lose when you lose weight. That's pretty crazy, but I don't know enough about the systems involved to discredit them.
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Old 01-24-08, 07:03 PM   #13
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If you actually took a four pound dump this morning, you have more urgent concerns.
+1 hear hear...
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Old 01-24-08, 07:31 PM   #14
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If the sheet you're using links critical power numbers to weight it's worthless. A backpack of lead does not change your FTP or CP.
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