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Riding with CycleOps PowerCal

20 July 2012 3 Comments
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UPDATE: There is a new post on PowerCal vs PowerTap comparisons.

…and…

About a year ago, CycleOps announced a revolutionary new device that would allow the calculation of power output during a bike ride through wearing a heart rate strap and nothing else. Back then, I wrote about it, and I was very skeptic.

Power meter product for cycling usually measure the force produce by the cyclist by using strain gauges on the crankset, on the pedals or on the rear hub.

The crankset based products, like SRM, Quarq and Power2Max, have been on the market longest and are usually seen as the most reliable and accurate, but the arguments always go back and forth with competing product like PowerTap which measures the force exerted on the rear hub of the bicycle. Obviously, the force exerted by the cyclist is slightly dissipated by the pedals, crankset and chain, which is why purists tend to prefer the crankset based power meters. However, most comparison tests place these within a small margin of error of each other. Finally the newcomer are the pedal based, which are still involved in a lot of product development and production delays and the only available on the market if the Polar/Look product. However, this one does not use ANT+ protocol, so it requires a head unit compatible with the proprietary transmission protocol used by polar. The vast majority of athletes use ANT+ cycling computers (like garmin, joule, timex, and others) so the absence of ANT+ is a big inconvenience.

Products like PowerCal calculated the power output through indirect methods (similar to iBike). In this case, CycleOps announced a product that would do it based on an algorithm derived from the heart rate. Note that there is a HUGE difference in price, whereas the other product typically cost between $1000 and $3000, PowerCal was first announced at $200 and was finally launched at $100…. This should temper your expectation on the capabilities of the product in terms of accuracy…

So, finally, a year later, the product is in the market (unlike some other products, like the Garmin Vector), but … is it any good?

IMG_0948

The first thing to notice was that the price came down from the initially announced at $199 and is now selling at $99. This is a good thing, but it is an indicator of the expect performance of the product.

I have ordered the product and it arrived quickly and I couldn’t wait to give it a test.

After reading through the documentation (almost none) and FAQ on the web site, CycleOps is very clear advertising that this is a product that is not competing with any power meter, rather just offering capabilities to calculate power and allow athlete to ‘dip their toes’ into power training rather than the more traditional heart rate based training.

In their own words, they announced that ‘PowerCal is not as accurate as a PowerTap and not intended to replace one.  Research has shown varying degrees of accuracy based on individuals and types of riding. Accuracy will depend greatly on the individual and type of riding.’

The power meter PowerTap from CycleOps measures power through strain gauges on the rear hub of the bicyle and is a direct measurement of power. PowerCal gives an estimated value derived from HR variation and this is based on the correlation between HR and power.

In my last year’s article, I’ve analyzed several rides and concluded that it would be almost impossible to established a direct correlation between HR and Power. However, cycleops is not using a simple correlation, but rather a complex algorithm that takes into account botht he heart rate, but more importantly the hear rate variability, ie, how quick or slow the heart rate is changing in response to effort. Here is where they get interesting results…

IMG_0945

For the tests, I’ve used my road bike where I have a PowerTap wheel using the latest PowerTap hub the G3.

On my  bike, I mounted my usual Garmin Edge 800, as well as a Garmin FR310XT.

The Edge 800 was paired to the PowerTap G3 hub and the FR 310XT was paired to the PowerCal heart rate strap.

Both were paired with the heart rate strap, to pick the heart rate information from a common source (and wearing two heart rate straps is just too bulky and unnecessary).

After making this setup, I hit the road, and started riding to compare the readings between the two with respect to power.

The first impressions confirmed the expectation that were set, even by CycleOps… The product is not intended to replace a power meter, or to compete with one. It simply provides a calculation for power based on HR.

During the ride, the power readings rarely agreed, but more importantly were always related, ie, the power calculated by PowerCal was always close to the power indicated by the PowerTap. The PowerCal algorithm does a great job at estimating the power output, based simply on the heart rate readings, and although never exactly the same, it gave a good indication of the actual power produced.

The main reason for power training has to do with the ‘slowness’ to react of the heart rate to actual effort, ie, even when producing a hard effort, heart rate may take 30 seconds or even a minute to raise in response to the effort.

The most important note, is that this not the case with the power reading from PowerCal. It reacts almost instantly to the effort, and within seconds of the power reading from the PowerTap. This was a very important conclusion during the ride, and allows some early conclusion as to the validity and usefulness of this product… It is BETTER than training with heart rate alone !!!!

Naturally, due to margin of error, not as good as training with power meter, but it is not even meant to compete or replace a power meter… so, even during the ride, I was already favorably impressed by this product.

After the end of the ride, I’ve compared the results from both power readings, by uploading them both to Training Peaks:

image  image

The PowerTap indicate an Average Power of 165W, and PowerCal of 175W

The PowerTap indicate a Normalized Power of 198W, and PowerCal of 206W

These numbers are incredibly close considering the cost difference between PowerCal ($99) and PowerTap G3 ($1300). As mentioned… not intended to replace a power meter due to margin of error, but still a very indicative number.

The Tables below compare the power average among several segments along the way on the ride, as measured by PowerTap and calculated by PowerCal:

POWERTAP:

image

POWERCAL:

image

Again, the numbers are incredibly close to each other, some segments showing a great margin of error than others.

Some segments the difference is +40W, in others –30W, but still, overall, I’m VERY impressed with these numbers.

There is more analysis to be made, more rides are required to understand what type of riding leads to more reliable and accurate results than other, but the first impression is very positive.

In conclusion, I’d say… that PowerCal is a really interesting product, trying to calculate power from heart rate. The advantages are obvious, the price, the ability to use it anywhere, and on any bike, including spinning bikes, indoors, etc… It provides a much better indicator of current effort than heart rate (on short intervals, since on long intervals heart rate will catch up with effort).

The power that it calculates and is displayed on the cycling computer constitutes, more importantly than viewing it as an objectively accurate number, it is a very good indicator of current effort. In that view, if you are too uncomfortable with the margin of error, think of it as Heart Rate Plus instead of Power… either way it is an improvement on the heart rate number !!!

So… Is it going to replace a power meter? NO Is it better than training only with heart rate information? YES !!!!!!!!!!!

In my view, if you have a power meter, don’t rush to get it, although you’d be able to use it at the gym. On the other hand, Given the price point, If you are replacing a heart rate strap, and are curious about training with power… Go buy it !!!!!!

 

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