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Does anyone know whether you consider bike weight when calculating a riders power to weight ratio?
 

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Depends..

If you are getting a VO2 max test done in the lab, the exercise physiologist will figure your aerobic power/weight ratio (ml of oxygen per kilogram, per minute) without considering bike weight of course. However, if you are trying to figure how fast you can get up Palomar Mountain, you would certainly consider bike weight.

Mike
 

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If you're calculating you power-to-weight ratio strictly in terms of physics, your weight is yourself plus the weight of the bicycle.

Pros trying to figure out how their training is coming along ignore the weight of the bicycle. The assumption is that at the higher levels of the sport, all bicycles will pretty much weigh the same - just at or over the UCI limit. So if you're trying to compare yourself to the pros, ignore the weight of the bicycle.

Power is always expressed in watt, weight in kilogram. If you're able to sustain 300 watt and weigh 80 kilogram, your "cycling" power-to-weight ratio is 300 divided by 80 = 3.75. For what it's worth, some pros at the very top level try to reach a ratio of 6 and over. I've read recently that the magic number L. Armstrong looked for in 2004 was 6.7.
 

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wim said:
Power is always expressed in watt, weight in kilogram.
Is that a law or something? If I say my power/weight is 0.002 horsepower/lb (useful for comparing to motor vehicles for example) do I explode or something. W/kg is the most common form but any set of units can be used.
 

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No law, of course. But this being a cycling forum, and cyclists expressing their power-to-weight ratio in watt per kilogram, the word "always" wasn't a bad choice. If you want to argue international standardization of weights and measures, knock yourself out :)
 

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How you specify the power. There was another thread here about this recently.
That's a good point. I believe power for a power-to-weight calculation is sustainable power - meaning a level of power that can be held for some length of time and not just for a brief sprint. How much time exactly? I don't know. Perhaps the time it takes to climb Alped'Huez.
 

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wim said:
That's a good point. I believe power for a power-to-weight calculation is sustainable power - meaning a level of power that can be held for some length of time and not just for a brief sprint. How much time exactly? I don't know. Perhaps the time it takes to climb Alped'Huez.

It depends. Often it is power at LT (which has a few different definitions, semantics aside, that will affect the power number). Seems a popular method with folks who don't have the equipment to test for blood lactate is sustainable power over a 20-30 minute time period. You could always do it for shorter time periods if the climbs you race are typically only a few minutes long.
 

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Often it is power at LT
Thanks, I didn't think of that. It makes sense to have the numbers come from the body doing the work, rather than set a vaguely defined period of time.
 
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