Introducing PowerCal a new kind of Power Meter

[BicyclePower]

This bring me back to a question I asked a while ago. What is your "input" into this to get it to gauge power for your HR values? Surely you have to at least supply your HR max...(?) (Since I understand this no longer requires calibration of sort, but that may be me misunderstanding it to begin with.)

 

no max HR needs to be entered, its just a case of put it on and off you go. no calibration what so ever.

[SeaBee]

Well that then confuses the daylights out of me. I somehow have a HR max which is quite high. You see my confusion? If this is HR based and I ride at 170, I am in zone 3 and far from maxing out, whereas Kiepie next to me is near cardiac arrest if he reaches 170, yet for us travelling along at the same effort and speed, he is then sitting at... say 150 or 155.

 

Trust me - I want to understand this, not undermine the product with my stupid reasonings. So don't get my motivation for asking the question wrong, please! I'd actually like to get one because it looks like something that will be good enough more likely than not for my use.

[El Dodgius Bastardo]

The only way I can see it working is if you do for a test which aligns heartrate to current power output every so often

 

Edit: I'd love to buy one, but have a geeks need to understand how it works

Edited July 26, 2012 by El Dodgius Bastardo

[BicyclePower]

Well that then confuses the daylights out of me. I somehow have a HR max which is quite high. You see my confusion? If this is HR based and I ride at 170, I am in zone 3 and far from maxing out, whereas Kiepie next to me is near cardiac arrest if he reaches 170, yet for us travelling along at the same effort and speed, he is then sitting at... say 150 or 155.

 

Trust me - I want to understand this, not undermine the product with my stupid reasonings. So don't get my motivation for asking the question wrong, please! I'd actually like to get one because it looks like something that will be good enough more likely than not for my use.

 

we welcome the questions and i will try be best to answer them.

 

here goes.

 

 

100 TSS points for you and 100 TSS points for MR Wiggo will mean it has the same intensity on each of your bodies. i.e. 1h at max!!

 

 

So that PC works in the same sort of way, try not look at the instant power values but rather the way in which the Power is scored. i.e. your mate and yourself are riding along at 30kph both at an intensity factor of .7 or 70% of FTP however your HR will be 170 and your friend 150 and because of this your powers will be different yet your IF will be the same.

 

 

The new Joule 1.0 and Joule GPS will both have an instant IF scoring.

 

 

Hope that helped.

 

http://home.trainingpeaks.com/land/what-is-tss.aspx

[Minion]

we welcome the questions and i will try be best to answer them.

 

here goes.

This seems to imply that the PowerCal would not necessarily give a good estimate of actual power, but would give a better estimate of IF and TSS. Is this what your testing shows?

[Barend de Arend]

The only way I can see it working is if you do for a test which aligns heartrate to current power output every so often

 

Power doesn't work like that. I can be at 150 HR and produce 0 watts, 250 watts, or 1000 watts.

 

Power is more closely aligned to the heartrate slope (ie. how quickly does it go up or down) When you go anaerobic there is another factor: the longer you stay anaerobic, the more your power drops. You've got fatigue. This is related more closely to the area under the graph than the graph itself. Welcome calculus.

 

In the example above:

0 watts: I was pedalling hard, got a high heartrate, and now I'm coasting. My HR hasn't reached rest yet.

250 watts: steady pedalling.

1000 watts: big burst (sprint?). My heartrate will go up in 10 seconds, and it will keep climbing for 30 seconds, but it hasn't moved yet.

 

Heartrate is also an indication of torque rather than power. It indicates effort rather than effect or work.

 

PowerCal has to look at movement in heartrate more than current heartrate. It's easy to get the 250 watt reading. If the heartrate is 150, and hasn't changed in the last 10 seconds, you can be pretty sure power is constant. PowerCal's magic juice has to differentiate between the 0 and 1000 watt cases. How well and quickly it does that will affect it's value. It is probably more accurate to calculate training dose or TSS or IF; but those aren't instant responses.

 

Heartrate might also go up when negotiating a technical downhill, but PowerCal will be able to compensate for that with a cadence sensor. No cadence = no power. All power meters already do this. Some power meter computers won't register power without a cadence reading.

 

How quickly your heartrate goes up and down is affected by your fitness, current health and whether or not you are warm, so the PowerCal algorithm has to take quite a lot into account. The accuracy is probably also affected by how rhythmic your heart beats. I'm quite interested in how well the magic juice performs.

 

If the magic juice is good, the value of the product will be high.

[SeaBee]

Thanks Barend - that helped me start understanding it a bit better...

 

Which means I'll most likely add cadence meter to mtb as well, which was something I was contemplating more for interest sake than anything else.

[BicyclePower]

This seems to imply that the PowerCal would not necessarily give a good estimate of actual power, but would give a better estimate of IF and TSS. Is this what your testing shows?

 

No this is not what I tried to explain, perhaps A better explanation would be as follows:

 

If both you and your mate are of the same weight, age, height and fitness and riding along at the same speed one would assume ur power would be very much identical. This would be someone correct if u were measuring power through a PowerTap however because there may or may not be changes in HR and using the PowerCal a power calculator based on HR this would not be the case.

 

Thus I suggested the TSS and IF ways of measuring efforts.

 

If as per your suggestion u say ur HR is 170 in zone 3 typical tempo session and the "average" person is 150 then ur power would then be higher however because u will then also have a higher HR at max efforts such as a 20min effort your power would then also be higher thus using TSS and IF as training factors would be ideal.

 

We can't say the PowerCal offers a 10% accuracy level across the range. Thus a 20min effort to establish FPT power is critical just as u would do with a PowerTap.

 

Once zones are established the powerCals reading are specific to u and u one. And not making them compatible to anyone else due to the above mentioned reasons in HR differences

 

I hope this helps?

[BicyclePower]

 

Heartrate might also go up when negotiating a technical downhill, but PowerCal will be able to compensate for that with a cadence sensor. No cadence = no power. All power meters already do this. Some power meter computers won't register power without a cadence reading.

 

 

 

the PowerCals algorithm does not take into account speed or cadence only HR i.e. your current HR and its drift. so if you are at 70bpm the PC will know very little to no power is being producted however if you go from 70-140 in the space of 3min the algorithm will put that effort into a power reading something along the lines of a 300w output at a guess. however if you HR went from 70-140 in the space of 30sec it might think you were at a set of light and pull of very quickly to catch the bunch again and so align itself with an effort of 800w plus at a guess.

[Minion]

I hope this helps?

I currently ride with a Quarq and Powertap on my road bikes. I plan to start MTBing again, often enough that it will have a significant effect on my cumulative TSS, but not often enough that I could justify the cost of a brand new MTB power meter. My HR strap is also on its way out, so a PowerCal could be a viable replacement.

 

In this scenario, I would be looking to combine the 'relative' power values from a PowerCal with the absolute values from the Quarq and PT in my overall TSS calculation. My concern is that while the PowerCal may give reasonable TSS and IF values when used in isolation and compared only with other PowerCal values, the estimation may not be acceptable as I'd be using it together with sessions with directly measured power values.

 

On a technical note, for my own curiosity, do you know whether it uses HR variability in it's estimation (there's quite a bit of ergonomic research that indicates HRV might be a good estimator of task effort).

[BicyclePower]

I currently ride with a Quarq and Powertap on my road bikes. I plan to start MTBing again, often enough that it will have a significant effect on my cumulative TSS, but not often enough that I could justify the cost of a brand new MTB power meter. My HR strap is also on its way out, so a PowerCal could be a viable replacement.

 

In this scenario, I would be looking to combine the 'relative' power values from a PowerCal with the absolute values from the Quarq and PT in my overall TSS calculation. My concern is that while the PowerCal may give reasonable TSS and IF values when used in isolation and compared only with other PowerCal values, the estimation may not be acceptable as I'd be using it together with sessions with directly measured power values.

 

On a technical note, for my own curiosity, do you know whether it uses HR variability in it's estimation (there's quite a bit of ergonomic research that indicates HRV might be a good estimator of task effort).

 

from the conversation i have had with the States i have been told it does, it uses current, instant HR as well as HR varibility

[BicyclePower]

morning everyone, got some good results this weekend, will try upload some files and graphs for you to view however in the mean time please look at the below links:

 

P.S. the order of the PC's left yesterday from the states, due to arrive very very soon!!!!

 

http://teamrodrigo.com/2012/07/20/riding-with-cycleops-powercal/

 

http://teamrodrigo.com/2012/07/23/comparing-power-readings-from-powercal-and-powertap/

[BicyclePower]

guys and girls,

 

please see the attached pictures of a .jpeg image of my 2 rides this past weekend. the PCwas within 5% of the PT readings!!!!

 

however whats more important is the trends of the graph. when power on the PT goes up so does the PC. and if only training on HR this would not be possible to note on shorter efforts.

 

i have the .csv files if anyone would like to view in PowerAgent or WKO.

 

PowerTap graph

 

 

 

 

PowerCal graph

 

 

[Minion]

guys and girls,

 

please see the attached pictures of a .jpeg image of my 2 rides this past weekend. the PCwas within 5% of the PT readings!!!!

I see the TSS value for the PC is around 15% lower than the PT. Is this a consistent trend across your rides? Also, is the difference in powers consistent, or is the PC sometimes higher than the PT?

[Cyclewizz]

 

What is more scary is the discrepancy in the two Garmin's Elevation recording! over 1000ft out.

 

I agree. If you read those articles you'd see the 2 Garmin's were different on everything.

[BicyclePower]

I see the TSS value for the PC is around 15% lower than the PT. Is this a consistent trend across your rides? Also, is the difference in powers consistent, or is the PC sometimes higher than the PT?

 

 

I am finding that the Power readings are a constant 10-15% lower than the PT however this is where the value of the PC comes in. because it is almost custom to each user due to HR changes etc one could decide to add10% onto each value however I don’t think this would be needed as the target market is more for the recreational rider who wants to track fitness and feels HR is just not sufficient and for around R1000 this is what the product has been designed for.

 

 

However for the more serious riders who want to keep track of fitness with PMC (performance management charts) then they could find out just how much off the PC is then add a fixed percentage. i.e. in my case add 10% to TSS and energy etc.

 

 

TSS will be affected due to the differences in normalized power, here the differences may be a little more because there are a lot more measurable involved in the normalized power calculation.