Tuesday, February 1, 2011

The ergomo power meter

I got my first Ergomo Pro power meter in 2005. I had it installed on my Griffen Vulcan triathlon bike and have been using it ever since. Most often I use it with the bike on the trainer but I also record my races and from time to time, my training rides. I use ismarttrain software on my Macintosh to retrieve the data. I analyze the data in Excel. It works like a charm.

For my USA Cycling power exam -which still isn't graded apparently- I had to use WKO and Trainingpeaks. It was not a pleasant experience and I can only say that Windows users must have a very high tolerance for poorly written software if they like this stuff. I for one, will stick with Excel. But back to Ergomo.

In 2007, after the German parent company got in trouble and cheap Ergomo units became available on eBay, I bought a few more and these I have used on and off on a road bike. At that time it was pretty easy to get a NIB Ergomo for around $300. The parent company went bankrupt and it seemed the end was near.

Last year, the Ergomo IP and assets were taken over by a Colorado outfit and they have since started to add new units and new features. My older Ergomo had a near-dead battery and I sent it to them to have it fixed. It came back, refurbished, with new battery and new seals and works perfectly. Even though the Ergomo brand is alive again, people continue to dump older units on eBay. Prices have risen somewhat from the low of $300, but it is still possible to get a first rate power meter for less than $700. Given how pricey SRM is, it is a steal.

The Ergomo had some early adopters, including Hunter Allen, Mr Power himself, who was an adviser to the company. Since then Mr. Allen has moved on and he is now a clear proponent of SRM. In spite of this early association with the driving force of power meter use, Ergomo never really "made it" to the big leagues. Nevertheless, the Ergomo is a high quality unit that is maintenance-free, very durable, extremely weather-resistant and long lasting. It is every bit as good and useful as the overpriced SRM.

The reason Ergomo never took off has a lot to do with the fact that it has been plagued by two issues since its inception. The first is really not an issue at all but it loomed big in the minds of Freds everywhere. It has to do with how the unit reads power.

Ergomo measures the torque in the bottom bracket axle. That is in many ways an ideal place for measurements and it has several advantages. It can be done friction-less, with minimal additional weight (the Ergomo pickup is optical and the weight penalty is totally negligble), and it also offers the best protection from the elements. You can literally drag the Ergomo through the mud without any issues whatsoever. That is one thing Mr Allen acknowledged when he showed his mountain bike (for Ruta) sporting an Ergomo.

Ergomo BB, square (Campy) type

The key worry is that the unit only measures the output from one leg (the left leg). The twisting of the axle (between the left crankarm and the right crankarm) is measured using an optical non-contact method. The value is doubled and plugged into an equation to get a power output. (No power loss but only half the effort is really measured)

For all practical purposes (and even scientific experiments) the one-leg measuement makes no difference whatsoever. But it really troubles the Freds, who have nothing better to do than to worry about such trifles. Even Mr. Hunter took it upon himself to joke that some people may have a monster left-leg that distorts the readings. "It happens, you know," he added. Maybe his new employer thought he should keep the doubt alive?

No asymmetry here

The second problem is related to the first. Just about the time that Ergomo hit the market, most component manufacturers switched (back) to the two piece crank with attached axle. Shimano led the way with HollowTech -as they usually do when it comes to gadgetry- but others soon followed. That move unfortunately, made the bottom bracket with axle look old-fashioned overnight. And perhaps more importantly, it made it so new cranks would no longer work with the Ergomo. I believe this played a big role in Ergomo's demise.

The component people also strongly advertised the benefits of the new two-piece crank. It was lighter and (magic word) stiffer, an attribute no Fred can ignore!

 It is perhaps ironic that before that time, two piece cranks were only found on cheap French bicycles. For decades the two piece crank had been the telltale sign of a cheap crank. But Shimano, a company that also tried to revive the non-round chainring (remember Biopace?) loves this type of innovation.

Remember those??

The Ergomo has a high quality display that is easy to customize. Although it is a tad big, it is easy to read and easy to use. The standard layout has two main screens and five secondary screens. On each screen there are four values. The unit can do metric and English (or even a combination of both).

You can display all kinds of information but the basic main layout shows power, heart rate, cadence and speed. There is an alternative main readout that shows altitude, % grade, power and speed.

Then there are four screens that contain additional information.  One of these has averages, the other maxima, the third calories and joules, with total distance and trip distance, and the fourth has analysis data.

For those who are really into power analysis, the fourth screen shows power (Watt), Normalized Power (NP in Watts), Training Stress Score (TSS) and Intensity Factor (IF).  These measures will sound familiar to the aficionados of the Coggan-Allen literature.

On bike analysis
Normalized power is perhaps the most useful measure and even before I learned about Coggan and his research I had figured out how to use it (Being a mac user, I don't read manuals, nor do I buy books that explain gadgets to me.)

When I bought the Ergomo in 2006, I knew very little about Coggan and his work. I certainly did not know that his friend and co-worker Allen was an adviser to the company. A recent USA cycling coaching publication explained to me that Allen was the one who urged Coggan to "develop" IF and TSS. I never saw much use in these values and even now that I know what they are for, I hardly ever use them. TSS is nothing more than how tired you are, while IF tells you how hard you went.

Before I learned all this I just thought NP was a proprietary measure that Ergomo had developed.

What I did figure out quickly however, is that NP correlated well with my perceived effort. And later I noticed that it was very useful in time trialing (ironman is a long TT) to keep NP and average power as close together as possible. What that really means is that you stay aerobic as much as possible. Checking the average and the NP afterwards gives you a good indication of how well you did sticking to that rule. The reason you may want to check is because it is easy to go hard without noticing.

The final Ergomo screen shows how much battery power is left, how much recording time is left, and other household items.

For mac users, ismarttrain will not just download the data. It will also allow you to set all the values you need to set. The only thing you can't do on a Mac is to update the firmware. To do that you need a Windows box.

I forgot to tell you about intervals. If you like Ergomo can store intervals and keep them separate. It is something I never use but it is there in case you need it.

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