Among the most talked about products at last fall's Interbike tradeshow - the Stages Cycling Power Meter - is slated to start shipping to shops and consumers this week. If it can deliver on it's significant promise, it could mark a huge sea change in the power meter market, substantially lowering the price and weight associated with strain gage-based power measuring systems.

Last week, the Boulder, Colorado-based company gathered about a dozen members of the cycling media to conduct initial test rides and go over final thoughts and figures relating to the new product. was on hand. Here are the highlights of what we learned.

What it is
In a nutshell, it's a power measuring device manufactured in Colorado that's affixed to the inside of a bike's non-drive side crank arm, and uses strain gages to determine power output by measuring deflection (aka extremely subtle microscopic bending) of said crank under load. Each strain gage is specifically calibrated to the crank it's mounted on.

The unit takes 64 discrete measures per second, which is far more than necessary for road riding, but could have interesting applications in the track, BMX and even downhill mountain biking world where rapid acceleration is key to success.

All that information is then doubled to account for the fact that it's measuring just one leg, then transmitted to the receiving device of your choice (Garmin head unit, iPhone, etc.) via ANT+ or Bluetooth technology. There's also an inboard accelerometer to measure speed and cadence.

It should be noted that Stages does not sell any of these recipient devices, just the non-drive side cranks with device affixed, or full cranksets with device. Also, the system only works with alloy cranks, which bend at a consistent rate, versus carbon with its mix of materials that do not bend uniformly.

That's no problem for Shimano users who can choose from nine different cranks, including Dura-Ace 9000 and Saint. But SRAM Red or Force aficionados will have to drop down to Rival. This was the case with the test set-up. We had the SRAM Red 50x34 carbon compact set-up removed from our road bike, and replaced with a SRAM Rival set-up including the new power meter and a BB30 adapter made by Wheels Manufacturing. The net effect was a 154-gram weight penalty (from 624 grams to 778 grams).

Stages says it is currently working on a better BB30 solution, which will utilize Cannondale's various BB30 cranks. But that wont be available until later in the spring at the earliest. You can see the full line-up of current offerings, including available lengths and colors here.

FSA and Campagnolo are not among the choices and from what we heard during the two-day press event, it doesn't sound like that will change anytime soon.

According to Stages marketing man Matt Pacocha, the unit works with "about 90 percent of the road bike frames on the market. It just depends on the location of the rear brake. It can be an issue with some lower priced time trial bikes, which use a full-sized caliper on the chainstay."

Stages does not retrofit its product on previously purchased crank arms, so don't bother asking if you can stop by Boulder HQ with your old crank in tow. The answer is, no.

The unit is powered by a CR2032 battery, which will cost you about a dollar at the grocery store. Run time is claimed to be 200 hours, with accuracy pegged at +/- 2% when measured at 100 watts and 90rpm. Occasional free firmware updates will be delivered via Bluetooth by way of the Stages Cycling Utility App, which will be available soon.

The Stages cycling power meter also includes a built-in thermometer, which feeds info into the main calculation so temperature change does not effect accuracy.

Some may question the accuracy of measuring just one leg. But Stages did its best to dismiss this concern, bringing in well-regarded cycling coach Neal Henderson, who's the sports science manager at the Boulder Center for Sports Medicine. Serving as an expert witness of sorts, Henderson said he rarely sees significant output differences between legs, and it's usually with patients who have had a knee or hip replacement, or some other significant body change.

Henderson also said he'd been doing some testing with the Stages Power meter and liked what he saw, writing on Twitter, "I'm impressed with ‪@stagescycling so far. Simple use, very light weight, consistent data, & very close to other validated PMs." You can read more of what Coach Neal had to say on his Twitter stream and see links to his various power files.

Price & Weight
Prices on the Stages Cycling power meter start at $700 (SRAM Rival, SRAM X9) and climb to $900 for Shimano Dura-Ace, XTR and Saint. The Cannondale Hollowgram models will run $50 to $100 more than Dura-Ace when they become available in the spring.

The power meter can be purchased via the Stages Cycling website, or at select independent bike shops. Purchase price also includes a 1-month premium subscription to both TrainingPeaks and Strava, roughly a $26 value.

By comparison, the least expensive PowerTap model runs $899, but that's just for the hub. You still need to build up a wheel, which you will then be locked into if you want to ride/train/race with power. SRM and Quarq don't restrict wheel choice, but the least expensive model is the recently-introduced Quarq RIKEN, which retails for about $1600. Prices of SRM and Quarq quickly rise into the $2000 range.

We didn't actually get a chance to weigh one of the Stages units ourselves, but claimed weight is "under 20 grams" and senior VP Pat Warner said that most units are closer to 14 grams. The weight hit for PowerTap models is in the 100-gram range, while spider-based systems typically add around 30 grams.

The variance in weight for the Stages system is due to the difference in protective housing shape from one crank model to the next. This housing is bonded onto the crank using a proprietary method that Stages claims does no damage to the crank itself, and creates a bond so strong that the two pieces effectively become one. That means it's totally waterproof, though Stages warns that it should not be directly sprayed with a pressure washer so cross racers need to be careful.

Each power meter comes with a one year warranty, and a longer warranty (think Apple Care) can be purchased for $105 to $135 depending on the model you choose. This could be a wise choice for mountain bikers and cyclocross racers, who run a much greater risk of suffering a direct-impact rock strike or crashing.

Does It Work
The short answer is, yes, it certainly appears to. During our time with Stages, they showed off all manner of charts and graphs illustrating that their simplified system, measuring just one leg, then extrapolating that data to account for total rider output was just as accurate as the popular hub and spider-based models.

We also ventured out on several test rides, including an all-out effort up Boulder's iconic Flagstaff climb. The goal here was to obtain a max 20-minute average, which could then be used to set up training zones with our new TrainingPeaks or Strava accounts. Based on personal prior experience (I've ridden the climb dozens of times) and current fitness level, my 279-watt average seemed about right.

But obviously that is by no means a true scientific test. Stages acknowledged this and encouraged all the media in attendance to do their own side-by-side testing.

Stages also claimed that they have done extensive in-house comparison analysis, with several staffers spending more than a year with three separate power meters running on their bike at the same time. When all three devices were calibrated properly (something many users forget to do), they claimed the variance was well within an acceptable range. But things like drastic temperature change and not doing a zero reset before rides delivered greater discrepancies.

"Side by side testing is not as easy as it might sound," said Warner, noting that even using one power meter with two Garmin head units can deliver varied information. "It can be a very frustrating process."

Who Is Stages
The company is new, but the people behind it are primarily industry veterans, with the core group having worked together for nearly 20 years, dating back to their time with Schwinn in the mid-1990s. "We are leveraging what we've learned along the way," explained VP Doug Crawford. "This not our first product, nor our first leap into product development."

"Within this group, we have 225 patents," added Warner, who was one of the riders who used the triple-power meter set-up during the company's testing and development phase.

For whatever it's worth, they all ride a ton, too. Company staffers' list of bike racing achievements include Ironman Kona finishes, Colorado state road and cyclocross championship wins, and national track racing titles. The daily group rides were spirited to say the least.

Why Would You Want One
Seven hundred dollars is no small drop in the bucket, but for anyone who's lusted after a power meter, but been chased away by the price, this might change the equation. Beyond that, the benefits of training with power are well documented. Unlike heart rate, which can be effected by everything from how hot it is, to how many beers you had the night before, power is quantifiable raw data that shows the rate at which you can do work.

Remember the famous watts/kg conversations that surrounded Lance Armstrong and what it took to win the Tour de France. Well, this is how you figure that out. I cranked out a whopping 3.5 w/kg during my aforementioned Flagstaff time trial effort. Rory Sutherland, who won the Flagstaff stage at last summer's USA Pro Cycling Challenge, knocked the 2.8-mile climb off by pumping out 6.8 w/kg.

There's also talk at Stages that this power meter could open the door to interesting applications in the mountain biking world. The company has signed sponsorship agreements with the SCOTT-3Rox and Yeti mountain bike teams, and Yeti's top brass, Chris Conroy, has expressed interest in how the device might be used to "test the effectiveness of new suspension designs and set-ups."

One final note. I've done my best to address as many potential questions as possible with this new product summation. But if you have any further questions, post them in the comments section below and I'll do my best to get you an answer. And of course, in the coming months we'll do further testing on our Stages Cycling power meter and let you know how it goes.