# CycleOps PowerCal



## wgeorge111 (Nov 27, 2010)

Does anyone know anything about this power meter caculated from heart rate CycleOps PowerCal? The price is nice for $199.00. Hopefully there will be more info following Interbike.


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## JustTooBig (Aug 11, 2005)

It's a calculation, which tells you most of what you need to know. Calculated values are notoriously inaccurate.

Direct measurement = much higher accuracy.

Calculated value = not so much.


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## Kerry Irons (Feb 25, 2002)

*Calculation*



wgeorge111 said:


> Does anyone know anything about this power meter caculated from heart rate CycleOps PowerCal? The price is nice for $199.00. Hopefully there will be more info following Interbike.


As JustTooBig noted, these kinds of calculations are notoriously innacurate. Even if you had a calibration curve that you developed yourself from a power meter plus heart rate measurements, your HR can easily vary 5-10 beats from one day to the next due to your level of hydration, how well rested you are, and ambient temperature.


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## multirider (Nov 5, 2007)

Kind of strange that CycleOps has a full page ad in magazines and nothing on their web site. I was thinking it might be useful for people who have multiple bikes, have an SRM or whatever on one bike, and would like to collect power data for ATL, CTL, and TSB tracking. 

It will be interesting to see how the thing works out for short intervals. In addition to the many factors that affect HR (sleep, stress, hydration, ambient temperature, humidity, etc),HR is a trailing indicator. I can start pumping out 125% of FTP without my HR responding for 30 seconds or more. So how would this thing recognize the new power output if my HR hasn't started moving yet? Similarly, if I'm at FTP for 20 minutes and then stop pedaling, my HR continues a bit before starting to recover.


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## Mr. Jones (Jul 4, 2006)

JustTooBig said:


> It's a calculation, which tells you most of what you need to know. Calculated values are notoriously inaccurate.
> 
> Direct measurement = much higher accuracy.
> 
> Calculated value = not so much.


They now have a video on their website that talks about how their calculations are super accurate and how in the lab heart rate perfectly predicts power. (They even have a fancy graph). I wonder how much manipulation they had to do to get that graph to look like that, or if they just made it up.


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## LouisVuitton (Aug 31, 2009)

Don't buy it. It's not worth it because it's not a real power meter


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## Coolhand (Jul 28, 2002)

Every guestometer like this tend to be a failure once people use them. And $200 isn't cheap either.


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## Alaska Mike (Sep 28, 2008)

Like the trainer charts that derive power from wheel speed. On the trainer, they work just fine and are kinda-sorta accurate. On the road (which they aren't designed for), they are nowhere near accurate.

If you take a ProTour rider and an untrained rider of the same weight and have them ride on the stationary trainer with the same heart rate, I bet you'd find a widely different power level. Just sayin'.


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## Undecided (Apr 2, 2007)

Alaska Mike said:


> Like the trainer charts that derive power from wheel speed. On the trainer, they work just fine and are kinda-sorta accurate. On the road (which they aren't designed for), they are nowhere near accurate.
> 
> If you take a ProTour rider and an untrained rider of the same weight and have them ride on the stationary trainer with the same heart rate, I bet you'd find a widely different power level. Just sayin'.


Not sure why this thread is back, but the PowerCal does have a major difference from other HR-based estimates of output, in that rather than reflecting assumed HR-calorie and HR-power relationships based on the averages from some population, it is calibrated by mapping the individual user's HR response against the measured power outputs in a particular workout (so the user needs to first use it with a power meter, or at a power-meter equipped stationary bike, to get it set up). I'm sure it's not 100% accurate, but I have enough years of power and HR data to think that it could work very well, assuming the user re-tests with a power meter as his or her fitness changes. Other than when I'm sick or tired, there's a pretty tight correlation between my HR and power for any relatively static effort beyond a sprint during any consecutive few months. One downside I see for it is that one of the things I like about a power meter is that when my HR and power get out of wack, I can't lie to myself about needing a rest, and that's lost. Similarly, for WKO+, it would overstate TSS toward the end of a hard "on" portion of my training schedule. 

The thread is a good reminder that people are pretty set in their objections, though, without regard to whether they know what they're criticizing.


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## Alaska Mike (Sep 28, 2008)

But that correlation between heart rate and power is where I think the problem is. As Allen Lim pointed out, “The power meter gives us an objective reference for what is actually happening in a given race or training ride while heart rate and perceived exertion allow us to understand how that rider is responding.” Both are effective ways of measuring effort, but come from completely different angles.

My issue with trying to compare the two is that heart rate can be so variable in relation to power, because of any of a number of variables. It's entirely possible to have your heart rate spike significantly without any increase in power- especially in a dynamic environment like the street.

With power meter prices on the retail market becoming more reasonable, and so many used power meters out there for sale, I find the pseudo power meters to make even less sense, except in an eWang sort of way. 

If you want to train by heart rate, train by heart rate. Nothing wrong with that. Just don't try to make it something that it's not.


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## Undecided (Apr 2, 2007)

Alaska Mike said:


> But that correlation between heart rate and power is where I think the problem is. As Allen Lim pointed out, “The power meter gives us an objective reference for what is actually happening in a given race or training ride while heart rate and perceived exertion allow us to understand how that rider is responding.”


I didn't see that as your original objection ("If you take a ProTour rider and an untrained rider of the same weight and have them ride on the stationary trainer with the same heart rate, I bet you'd find a widely different power level. Just sayin'."), and I don't disagree that there can be short-term variance in the relationship between HR and power because of other factors. As I said before, though, I could see it being fairly close for longer efforts (based on my personal HR and power data; I wonder how large Cycleops' data set is). And I agree with you about someone just training by HR if s/he's not going to get a "real" power meter. I'm probably an outlier, but I've been thinking about getting one of the Cycleops' units as a supplement to my primary (power) training, just for the convenience of using it to feed the data into WKO+ when I travel (when I use either a backup bike that I leave at the place I go to most often, or rent a bike), to more conveniently keep track of TSS. That use probably isn't a huge market . . . .


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## Alaska Mike (Sep 28, 2008)

Probably not the best way to state my opinion, for sure.

Let's take it a little further. Tracking heart rate and power during intervals, they do somewhat gel. However, on longer, harder intervals my heart rate starts low and ramps up over time for a given power level. On repeated VO2max intervals, my heart rate progressively climbs- even with a solid recovery. Hydration, fatigue, temperature, and scores of other things can make my heart rate for a given power level fluctuate quite a bit- even in a "controlled" environment like on a trainer. While I was getting a benefit from these workouts, they weren't as effective as training with power. 

That said, there are more than a few rides where I don't track power and just go off of heart rate. Again, I shift my thinking from measuring what I'm putting into the pedals to how that effort is affect me.Two sides of the same coin, but they are different sides.

I track those workouts in WKO too. Maybe I don't get an IF or TSS, but I still see it as valuable data.


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## Undecided (Apr 2, 2007)

Alaska Mike said:


> I track those workouts in WKO too. Maybe I don't get an IF or TSS, but I still see it as valuable data.


Of course, but if you look at TSB in trying to time your peaks, the more gaps you have in TSS data (or the less accurate your TSS data is), the less useful TSB will be.


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## wgeorge111 (Nov 27, 2010)

I was looking a Cycleops web page to see what is going on with the Power Cal. I see the price has come down to $99.99 and you no longer have to calibrate it. Does anyone know why the changes form it supposed to be $199.99 and needing to be calibrated ?

http://www.cycleops.com/en/products/power-meters/powercal.html?page=shop.browse&category_id=25


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## bgmarc26 (May 15, 2007)

*Powercal review*

Just used my 99 dollar powercal today for the first time ! I will say this thing is just a guestamter for power readings. If you shave your legs and cut the tags of your jerseys to be lighter than this product is not for you. It's readings we're pretty dead on give or take 10% . The product is meant to get people interested in training with power with out going broke or getting a divorce in the process!


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## nightfend (Mar 15, 2009)

Without knowing your weight, or threshold power or anything, how could it possibly make a guess on your power numbers? I looked at their quickstart guide and it doesn't mention anything about inputing this data.

I mean, as someone stated, you could be a pro racer that has a threshold of 350 watts, or a beginner with a threshold of 200 watts. There is such a huge variance in power, I just don't see how it can even guess accurately.


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## bgmarc26 (May 15, 2007)

*It's not a powertap*

If u own a powertap or an srm try the powercal and compare the numbers. This device wasn't not meant to be specific. It's just meant to give the recreational cyclist an idea where his power might be. I understand with heart rate and power thresholds vary from cyclist to cyclist .


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## nightfend (Mar 15, 2009)

I don't mind the idea of mapping general power numbers to heart rate. It would make a fairly inexpensive and useful device for getting a general grasp on power while on a ride. But it still needs to be adjustable by the individual depending on their fitness, otherwise is is completely useless. From what I can tell from the online manual, there is no customization of any kind. So who knows what fitness they are basing the power numbers on.


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## Darren5311 (Jun 23, 2012)

Would it be useful to a user with no other power meter, just to compare training efforts and levels of improvement? And not to compare my power to anyone elses?


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## robdamanii (Feb 13, 2006)

It *might* be valuable assuming it was consistent. I can't imagine it's terribly consistent considering it bases power number on heart rate. Heart rate is so incredibly variable from so many influences that it's pretty useless. 

Additionally, HR is a measure of input, while power (measured power) is a measure of output.


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## zv2011 (Oct 10, 2011)

nightfend said:


> I don't mind the idea of mapping general power numbers to heart rate. It would make a fairly inexpensive and useful device for getting a general grasp on power while on a ride. But it still needs to be adjustable by the individual depending on their fitness, otherwise is is completely useless. From what I can tell from the online manual, there is no customization of any kind. So who knows what fitness they are basing the power numbers on.


^^this... i don't understand how this thing works. It has to take in something else other than heart rate.

For instance, a pro tour rider riding at 160bpm is putting out a metric crap ton more power than myself riding at 160bpm, so how does it make it's "guess" as to how much power? Is it using speed or something else?


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## arai_speed (Aug 19, 2003)

i wonder, is this product any more or less accurate than the power given by strava?


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## nightfend (Mar 15, 2009)

arai_speed said:


> i wonder, is this product any more or less accurate than the power given by strava?


Less, I guess. Because Strava at least takes into account the terrain gradient and rider weight.


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## Undecided (Apr 2, 2007)

wgeorge111 said:


> I was looking a Cycleops web page to see what is going on with the Power Cal. I see the price has come down to $99.99 and you no longer have to calibrate it. Does anyone know why the changes form it supposed to be $199.99 and needing to be calibrated ?
> 
> http://www.cycleops.com/en/products/power-meters/powercal.html?page=shop.browse&category_id=25


Very interesting that they abandoned the calibration (which, at least, was a qualitatively different approach from other HRM --> energy devices). 

From their FAQ:

_Why does it no longer have to be calibrated?

After years of research and reevaluation of the algorithm it was determined that the calibration process added no more accuracy than the algorithm alone. Due to the variability of heart rate, both between and among individuals, calibration did not statistically increase accuracy of translated energy expenditure. Some individuals may see improved accuracy through calibration but, as a whole, the results show the algorithm alone is able to translate heart rate to power as well as individual calibration. _

Surprising, and tough to believe. Not sure I want to buy one and a second ANT+ computer to test it out though.


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## MTBer4life (Dec 9, 2008)

DCRainmaker did test it along with other powermeters and found that while its real time power display was not very accurate, over the course of a ride it gave a fairly accurate average power output. So it would be good for comparing your average power over different rides but not for interval training.


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