# 2 questions..what tool do u use to analyze power data?



## nyvram (Apr 11, 2002)

i've figured out how to 'grab' an area in spottracks so i can see average power over a given interval..is there a better way to do it?

second, i've noticed when i'm doing a ride where i stay in the 53x13 the whole time (working on building leg strength) and i'm really redlining going up some of the hills..but the wattage is showing around 250. 

however if i'm spinning hard on some climbs i've seen it spike to 700. am i misunderstanding how my percieved effort ties to power output?? i would have said the effort of climbing a hill in a big gear is MUCH MUCH harder than spinning in a gear going 30mph.

i'm a newbie to power so be gentle..i did join the google group


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## JustTooBig (Aug 11, 2005)

1) maybe I missed it ..... what PM are you using? I use WKO+ for most analysis, but the built-in software that comes with the SRM PM's allows you to simply highlight any chosen interval within a workout and get power, HR, etc., for that interval. I have not tried that within WKO+ or any other analytical software.

2) Power = torque x velocity. When you're mashing that huge 53x13 gear, the torque may be really high, but the velocity (how fast the cranks -- or hub for a PT -- are turning) is very low. So .... low power reading, but the high torque applied fatigues you quickly -- and drives up your heart rate. 

Perceived effort doesn't always equate to power output because of the torque in the equation. High torque = high perceived effort. But if it occurs at a low cadence, the resulting power may not be that high. Does that make sense, or did I muddy the water?


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## Daren (Jul 25, 2008)

Golden Cheetah is a free program that has a few different tools from PowerAgent. I've not used WKO, so I don't know how it compares.


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## nyvram (Apr 11, 2002)

thanks! i was wondering if something was wrong with my powermeter.

i'm using a powertap SL+ (i think) and reading teh data into my garmin 500.

its the midrange wireless powertap..the one that isnt so dang heavy but i cant remember the model number.


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## the_gormandizer (May 12, 2006)

JustTooBig said:


> 1)So .... low power reading, but the high torque applied fatigues you quickly -- and drives up your heart rate.
> 
> Perceived effort doesn't always equate to power output because of the torque in the equation. High torque = high perceived effort. But if it occurs at a low cadence, the resulting power may not be that high. Does that make sense, or did I muddy the water?


The water seems quite muddy to me! Power also equals force times velocity. Force is (roughly) mass times gravitational acceleration on a climb --- or at least a vector component of it, combined with aerodynamic drag, rolling resistance, etc. The point is any given cyclist will need to produce a certain power to climb a hill at a given speed. As you say, power could either be produced by a low torque and high rpm, or vice versa. Low torque/high RPM might tax the cadiovascular system more, low RPM/high torgue will tax the leg muscles more. A cyclist will likely have some optimal cadence range for a given hill and given level of fatigue. Does this make sense?


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## JustTooBig (Aug 11, 2005)

the_gormandizer said:


> The water seems quite muddy to me! Power also equals force times velocity. Force is (roughly) mass times gravitational acceleration on a climb --- or at least a vector component of it, combined with aerodynamic drag, rolling resistance, etc. The point is any given cyclist will need to produce a certain power to climb a hill at a given speed. As you say, power could either be produced by a low torque and high rpm, or vice versa. Low torque/high RPM might tax the cadiovascular system more, low RPM/high torgue will tax the leg muscles more. A cyclist will likely have some optimal cadence range for a given hill and given level of fatigue. *Does this make sense*?


sure it makes sense. Are you asking for some kind of a clarification from me? The OP asked for a basic explaination of why his perceived effort was not always reflected in his power numbers. I attempted to provide that explaination. Maybe I did it poorly...


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## kbiker3111 (Nov 7, 2006)

nyvram said:


> thanks! i was wondering if something was wrong with my powermeter.
> 
> i'm using a powertap SL+ (i think) and reading teh data into my garmin 500.
> 
> its the midrange wireless powertap..the one that isnt so dang heavy but i cant remember the model number.


http://cycleops.com/products/power-meters.html?page=shop.browse&category_id=2


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## nyvram (Apr 11, 2002)

thanks...its the pro+


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## dwgranda (Sep 8, 2009)

700 is possibly not a useful number to compare perceived effort, especially with the 250 number. They likely happen in 2 different situations. I'm guessing you can hang around 250 for quite awhile and 700 for less than 30 seconds (probably a lot less than 30 seconds). Now to get a reading of 700 for 2-3 seconds going on a slight downhill when you're accelerating (just one example I can think of) and already going pretty fast won't have a very high perceived effort and you don't need to be a stud cyclist. Doing 700 for 30 seconds should have a VERY high perceived effort. Does that add any insight?


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## ericm979 (Jun 26, 2005)

GoldenCheetah can read the .fit files off a Garmin 500. It works well.


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## nyvram (Apr 11, 2002)

thank you all! every comment makes perfect sense. i had a feeling as i was barely turning the cranks over that it seemed logical the power meter wasn't showing much. your explanation about torque vs. effort makes complete sense.

yeah i'm not trying to worry about my max wattage..just trying to make sure i understand what is going on so i can do a fit test this week to prepare for training.

oh..while i'm thninking about it..i'm confused about calibration.

i read something that said putting your foot on the pedal while 'zeroing' the garmin but then it seems that was old info and now you just make sure the bike isn't moving when you 'zero' it and thats all you have to do. is that right?

also do i need to perform this step before each ride or do you generally only calibrate once a ..week? ...month? year?


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## dwgranda (Sep 8, 2009)

Powertap calibration is never done with the pedal weighted. You can check calibration by putting a known weight on the pedal and looking at the torque value. Since you know the distance the weight is acting on you should be able to calculate what value you should see on the computer.

Also the "calibration" most people refer to is a zeroing of your computer. I don't believe the value sent by the powertap depends on the computer zeroing. So you might find it useful if you suspect your power numbers are off to do the static test I described above. That will tell you if your powertap is measuring correctly.


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## nyvram (Apr 11, 2002)

i'm not sure i follow. so lets say i put a 5lb weight on the pedal..when i 'reset' it on the garmin it zero's out. i'm not sure i can do anything more at that point. i thought i was trying to get this to zero while the bike wasn't moving..not sure i get what the weight does for me.


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## dwgranda (Sep 8, 2009)

nyvram said:


> i'm not sure i follow. so lets say i put a 5lb weight on the pedal..when i 'reset' it on the garmin it zero's out. i'm not sure i can do anything more at that point. i thought i was trying to get this to zero while the bike wasn't moving..not sure i get what the weight does for me.


You zero it first. Then put it into torque mode. Then place the weight on the pedal with crank arm parralel to the floor. You don't want the bike to move so set the brake or something. Work through the equation that depends on the weight you are using and your gearing. That will tell you what you should see on the computer. If it's way off, there's not much you can do except send it back. Google powertap static test if you're interested in the details of this test.


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## nyvram (Apr 11, 2002)

ok i got it..calibration and zeroing are 2 separate things. just read up a little more on the calibration equation. makes sense. i just need to find a 50lb weight now and a way to hang it ;-)

thanks! yes..i'm obsessive..i'd like to know if/how far off my powertap might be.


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## nyvram (Apr 11, 2002)

ericm979 said:


> GoldenCheetah can read the .fit files off a Garmin 500. It works well.


golden cheetah looks awesome. isn't someone on here involved in writing that utility or plugins for it?

i am getting analysis fatigue..importing into strava, ridewithgps, garmin connect and sporttracks is getting old. i need to find my favorite because i'm worn out entering and correcting data in all those sites


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## stevesbike (Jun 3, 2002)

just buy WKO. It has many, many more features than the others.


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