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Power Meters Heartrate Monitor
I came across the Powercal Power Meter device when I was looking around for a power meter. It is a heartrate monitor strap that extrapolates power based on (I can only assume) change in heart rate using some form of algorithm. There is no direct power meter on a hub, ledal or crank - its only input is heart rate.
What a load of rubbish I thought.
Then I read the comparison below where the Powercal heartrate power monitor was compared with a real power meter.
Interesting reading. I bought a Powercal and it connects via ANT+ to my Garmin 800 and give wattage readings. I have no iea how accurate they are (I'm relying heavily on the review as proof of concept) but it does give some viable looking power graphs.
http://bikehabit.blogspot.com.au/2012/07/cycleop...
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Looks pretty interesting. Currently $150-odd on wiggle. Might have to look at it when my current HR strap dies.
Nice, but what if one already has a HRM? Why buy another?
What you really need is some software (or an online service) that takes existing workout files and adds power based on heart-rate using their propriety algorithms. Or even better - that Garmin Connect or Strava license this and offer it to their members as an option?
Licensing the maths would solve that but I like seeing it in real time.
Good point about seeing it in real time. Hmmmm... so, stupid question:
If one buys one of these straps to work with an Edge 500... It sends power and HRM data to the unit? Like - you don't have to wear two straps? That would just be silly
Thats the impression i got from the review and the OEM website. It replaces your current strap and sends a power meter signal to your existing ANT+ head unit.
I'm guessing the heart rate sampling speed is much faster than the normal Garmin 3 seconds recording interval setting as it appears to use the delta to account for the lag in your HR when you drop the hammer.
The powercal sends out HRM and power data.
Not sure on frequency of data sending, but I can say it works as it should.
http://teamrodrigo.com/2011/06/27/the-case-for-c...
http://forums.roadbikereview.com/racing-training...
May help
Its a complete waste, IMHO.
Even an SRM power meter, crankset and HRM are only good guides to what is going on.
Extrapolating calorie consumption comes from weight, age, height and heart rate, on a basic HRM. Even then, it guesses critical data like muscle mass. The 'power' data comes from the calorie guesswork added to a delta (change) HR formula that they have come up with. It's a guess based on a guess.
From this device, if you have 2 people, same weight, age etc, when they work at the same heart rate, they will both use the same calories and produce the same power. Thats obviously rubbish because you could generate far more power than I can at the same HR, but the device will give the same result.
After all, thats the point of training with a power meter and HRM. Generate more power for the same or less heart rate.
You just can't reliably extrapolate power from HR. It's a toy to give you some cool graphs. Don't mistake it for a training tool.
The graphs may look fancy, and accurate, but on key figures, they are out over 25%. And thats compared to a pretty average Quark power meter. Compared to an SRM?
25% may not seem like much, but I can generate a measly 1,400w peak over 30sec. With a 25% error in my favour that puts me at 1,750w: Mark Cavendish territory, or 1,050w and im 13 years old again. Big difference.
Even worse, the Powercal is not consistently above or below.
On one point its 25% below (475 vs 600)
Then its 35% above (575 vs 425)
Its just all over the place.
For example, my lab results for max power and average over 30sec show UP TO 10% variation, and thats with 1 variable. Take out that variable and it's about 5% week to week.
25% +/- variation is just going to confuse the hell out of you.