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How many train with power?

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Mar 19, 2009
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Average power means squat in a race situation. Who's fastest is the only thing that matters. The criteria of course is different if you're going for hardest working cyclist of the year award or something.
 
Mar 12, 2009
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OJ.... said:
Average power means squat in a race situation. Who's fastest is the only thing that matters. The criteria of course is different if you're going for hardest working cyclist of the year award or something.

DURING the race, yes, avg power means little. Post-race analysis, however, and avg power, speed, hr, etc are extremely important.
 
Jul 27, 2009
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Tapeworm said:
DURING the race, yes, avg power means little. Post-race analysis, however, and avg power, speed, hr, etc are extremely important.

Not really. The analysis is only really meaningful if you can repeat it and compare on measureable comparable efforts. A race from one week to another is not really comparable, there are just too many variable factors.

A much more meaningful comparison is measuring individual efforts on pre-determined training courses and segments where the only variable is the weather.

In a race you’re only trying to win, not set training benchmarks.
 
Mar 12, 2009
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M Sport said:
Not really. The analysis is only really meaningful if you can repeat it and compare on measureable comparable efforts. A race from one week to another is not really comparable, there are just too many variable factors.

A much more meaningful comparison is measuring individual efforts on pre-determined training courses and segments where the only variable is the weather.

In a race you’re only trying to win, not set training benchmarks.

Ah no, the data from a race is important for variety of reason. I agree that it is not about setting benchmarks, however this can occur and training loads adjusted accordingly (ref: The Seven Deadly Sins for determining FTP). Similarly appropriate recovery/training load and refuelling strategies can utilised with such data.

Also if you have comparable data from multiple riders the data can be telling about positioning within the pack, aerodynamics etc.

Though for all of the above normalised power is of more relevance usually.

There is more to a powermeter than just trying to better your last effort on a certain bit of hill or a particular course.

Whilst AVG power is not usually relevant in races instantaneous power can be of benefit. Essential? No, but some like to see current power output and can be used to guide race strategy.
 
Jun 15, 2010
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Tapeworm said:
DURING the race, yes, avg power means little. Post-race analysis, however, and avg power, speed, hr, etc are extremely important.

Do power meters have to be tested periodically?Surely they go out of calibration over time.
 
simo1733 said:
Do power meters have to be tested periodically?Surely they go out of calibration over time.
It is a good idea to validate the accuracy of your power meter from time to time, or when you make a change to something in the drivetrain (like chainrings for instance).

Calibration is a relatively simple process that all the main units (SRM, Powertap, Quarq) enable you to do if you have the correct head unit. All you need is to be able to apply an accurately known torque to the pedals, typically done by hanging a known mass (which might be zero to 40kg say) from the pedal spindle on a horizontal crank arm and compare the known torque with what the power meter reports.

Fortunately, calibration tends not to drift much, it's usually when something goes especially wrong, that calibration moves a lot.

My SRMs have drifted <1% in slope calibration over many years of usage.

Only the SRM enable you to change the slope calibration setting should a change be detected.


Calibration is not to be confused with setting the torque zero, which needs to be performed before each ride and sometimes during a ride (whether by manual intervention or automatically by the power meter).

Analogy with bathroom scales:

Setting the zero is checking the scales read zero when there's nothing on them, and adjusting the zero setting if they don't quite read zero.

Calibration is validating that not only does the scale read zero when there's nothing on them, but they also read X.xx kg when you put an accurately known X.xx kg on them.
 
Jun 1, 2010
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Alex Simmons/RST said:
Calibration is a relatively simple process that all the main units (SRM, Powertap, Quarq) enable you to do if you have the correct head unit. All you need is to be able to apply an accurately known torque to the pedals, typically done by hanging a known mass (which might be zero to 40kg say) from the pedal spindle on a horizontal crank arm and compare the known torque with what the power meter reports.

.

Alex - can you explian in greater detail how you do the calibration with a Powertap? Is the bike in a stand and then say 10 kg hung of the pedal- giving an instantaneous force down and thus torque which you then check with the theorectical value (based on weight and crank length)?
 
microdose said:
Alex - can you explian in greater detail how you do the calibration with a Powertap? Is the bike in a stand and then say 10 kg hung of the pedal- giving an instantaneous force down and thus torque which you then check with the theorectical value (based on weight and crank length)?
Basically that's it, although I'd recommend a heavier mass, 20+kg* and hang from pedal spindle with crank horizontal (eye ball horizontal will do). If you are steady and bike is locked in trainer, and you know your own mass accurately, then you can balance your own weight on the pedal very carefully.

You'll need to be able to fix the rear wheel. Either a friend to hold the brakes, or something in the spokes to prevent it from rotating.

All you then need to know is the gear used (chainring & cog) and crank length and you can calculate the torque applied. Compare that to the reading shown in the torque display mode of the Powertap.

Make sure you zero the torque between each test (alternatively you can set the PT computer to show the torque numbers in the test mode - and then record the zero value which will be approx 512 and the loaded torque value - the difference being the torque value displayed in the torque mode - I prefer this way as it shows me if the torque zero point is changing between each check).

Torque is displayed in ft-lbs on a powertap.

So actual torque = mass in pounds (or kg x 2.2046) x crank length (mm) / 25.4 * cog teeth / chainring

So, for example:

44.1lbs (20.0kg) on 170mm cranks with chain in the 39x15
= 44.1 x 170 / 25.4 * 15 / 39
= 114 inch-pounds

Check displayed torque and see how close it is to the known applied torque.

Then repeat this 2-3 times to validate and also on some different chainring & cog combinations.


* if using a barbell weight, then get it accurately weighed on postal scales as they are notorious wrongly marked. I have weight marked "20kg" that actually weighs 19.5 kg.

I personally have 31kg of accurately know mass for when I perform calibration checks on SRM and Powertaps.
 
Jun 1, 2010
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Thanks Alex - sounds like quite a bit of work. It would probably be more beneficial for me to ride my bike more, but I may get around to it one day.
 
Jul 23, 2010
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Ive been training with more power............
DSCN3943.jpg

Screenshot2011-02-06at103230AM-1.png
 
Mar 10, 2009
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Michele said:
The new german Power2max doesnt allow calibration by what I understood.

I was searching the forum to find out if someone knew more about the power2max, but the queries only retrieved your (2?) posts. I am guessing no one has used the power2max yet. Is it only available in Europe?

EDIT> I did find this German test.
 
Bala Verde said:
I was searching the forum to find out if someone knew more about the power2max, but the queries only retrieved your (2?) posts. I am guessing no one has used the power2max yet. Is it only available in Europe?

EDIT> I did find this German test.

I am testing a pOwer2max for the NZ/AUS agent.

The cranks went together and went on smoothly. Paired well with my Garmin Edge 500 and from two indoor sessions and an outdoor session the power appears consistent with my Powertap. I get my Powertap back on Thursday and will do some comparison tests.
 
Mar 10, 2009
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sciguy said:

CoachFergie said:
I am testing a pOwer2max for the NZ/AUS agent.

The cranks went together and went on smoothly. Paired well with my Garmin Edge 500 and from two indoor sessions and an outdoor session the power appears consistent with my Powertap. I get my Powertap back on Thursday and will do some comparison tests.

Thank you both for your replies!

Let us know what your findings are...
 
Got a pair of pOwer2max cranks from European Sports Imports (bikecycle.co.nz) to test. Had loaned my Powertap to one of my riders but I have it back for the weekend while he gets smashed at Taranaki so have been doing some testing...

30sec test on rollers. Zeroed the Powertap with the Cervo head unit
and checked the calibration of the P2M (-885) with my Edge 500.
5sec
Avg Power P2M 359
Avg Power PT 369
10sec
P2M 355
PT 363
20sec
P2M 353
PT 357
30sec
P2M 348
PT 355

Raw files from importing from WKO+ to GC to easily cut and paste.

Time (sec) P2M Watts P2M Cad PT Watts PT Hub Cad
303 270 81 319 88
304 342 93 395 98
305 350 101 347 104
306 350 101 386 107
307 353 108 368 110
308 353 108 350 112
309 360 113 363 114
310 364 114 364 112
311 364 114 363 114
312 356 114 351 112
313 349 114 347 121
314 348 114 342 112
315 352 114 360 112
316 352 114 349 114
317 351 114 354 110
318 351 113 346 114
319 357 114 367 110
320 352 114 354 114
321 350 114 350 112
322 350 114 346 114
323 348 114 340 114
324 345 114 349 112
325 349 114 358 112
326 349 114 341 112
327 349 114 350 112
328 349 114 345 110
329 346 113 359 114
330 346 113 372 114
331 360 114 358 112
332 320 114 208 115
333 204 114 89 104

Better comparison between the Powertap and Power 2 Max on the road
where I did a uphill effort, a 20min effort and a 60sec effort.
Apologies for the sad totals but I spend more time analysing data than
generating it. Max difference 4 watts from the 3 efforts. For a 3rd of
the cost of a SRM or a 2/3rd the cost of a Powertap I could live with
that. Will do a MAP test tomorrow and then if I can still turn the
cranks will do a T-Max Test (time at MAP) and man up for some T-Max
intervals on Saturday.

Powertap Hill Effort
Duration: 3:30
Work: 55 kJ
Distance: 578 m

Min Max Avg
Power: 89 434 265 watts
Heart Rate: 149 172 166 bpm
Cadence: 53 104 60 rpm
Speed: 8.6 22.2 9.9 kph
Pace 2:42 6:59 6:03 min/km
Hub Torque: 0.9 4.7 3.3 N-m
Crank Torque: 11.3 59.2 42.8 N-m

Power 2 Max Hill Effort
Duration: 3:28
Work: 54 kJ
Distance: 564 m
Elevation Gain: 49 m
Elevation Loss: 0 m
Grade: 8.8 % (49 m)

Min Max Avg
Power: 108 415 263 watts
Heart Rate: 150 172 166 bpm
Cadence: 54 80 60 rpm
Speed: 6.1 19.6 9.5 kph
Pace 3:04 9:50 6:19 min/km
Altitude: 2 51 29 m
Crank Torque: 13.4 55.8 42.4 N-m
Temperature: 15 15 15.0 Celsius

Powertap 20min effort
Duration: 20:07
Work: 282 kJ
TSS: 32 (intensity factor 0.977)
Norm Power: 245
VI: 1.05
Distance: 11.005 km

Min Max Avg
Power: 0 485 234 watts
Heart Rate: 147 189 173 bpm
Cadence: 60 147 88 rpm
Speed: 15.9 51.5 32.7 kph
Pace 1:10 3:46 1:50 min/km
Hub Torque: 0 3.3 0.9 N-m
Crank Torque: 0 67.1 25.7 N-m

Power 2 Max 20min effort
Duration: 20:03
Work: 277 kJ
TSS: 31.1 (intensity factor 0.964)
Norm Power: 242
VI: 1.05
Pw:HR: -1.56%
Pa:HR: 0.3%
Distance: 10.883 km
Elevation Gain: 21 m
Elevation Loss: 27 m
Grade: -0.0 % (-4 m)

Min Max Avg
Power: 0 479 230 watts
Heart Rate: 148 189 173 bpm
Cadence: 61 98 88 rpm
Speed: 14.3 52.5 32.3 kph
Pace 1:09 4:12 1:51 min/km
Altitude: -2 19 4 m
Crank Torque: 0 67.9 25.3 N-m
Temperature: 14 15 14.1 Celsius

Powertap Peak 1min (452 watts):
Duration: 1:00
Work: 27 kJ
Distance: 681 m

Min Max Avg
Power: 160 1008 452 watts
Heart Rate: 157 196 186 bpm
Cadence: 78 117 96 rpm
Speed: 30.9 45.3 40.6 kph
Pace 1:19 1:57 1:29 min/km
Hub Torque: 0.5 3.5 1.3 N-m
Crank Torque: 17 119.2 45.1 N-m

Power 2 Max Peak 1min (453 watts):
Duration: 1:00
Work: 27 kJ
Distance: 678 m
Elevation Gain: 0 m
Elevation Loss: 0 m
Grade: 0.2 % (1 m)

Min Max Avg
Power: 230 955 453 watts
Heart Rate: 158 196 187 bpm
Cadence: 79 114 96 rpm
Speed: 34.4 47.7 40.2 kph
Pace 1:15 1:45 1:30 min/km
Altitude: -6 -3 -6 m
Crank Torque: 24.4 109.8 45.2 N-m
Temperature: 14 14 14.0 Celsius

Soon will have a Look pedal based power meter to play with as well. 3 power meters on the go at the same time, be still my inner geek.
 
If a power meter consistently reads low or high then it is still useful data on an individual basis. Have been doing some special trainings with several riders on power meters and one thing is for sure that power alone (even power to weight) does not give you the full picture when comparing riders. So for the price point of NZ$1895.00 (say Coach Ferg sent you for a discount) for the SRAM version (less for TA and more for Rotor) it is a great price for U19s and Masters level riders who don't need the awesomeness of SRM, Powertap or Quarg.
 
Jun 16, 2009
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CoachFergie said:
If a power meter consistently reads low or high then it is still useful data on an individual basis. Have been doing some special trainings with several riders on power meters and one thing is for sure that power alone (even power to weight) does not give you the full picture when comparing riders. So for the price point of NZ$1895.00 (say Coach Ferg sent you for a discount) for the SRAM version (less for TA and more for Rotor) it is a great price for U19s and Masters level riders who don't need the awesomeness of SRM, Powertap or Quarg.

Why so expensive? The basic unit is 630 euro.....
 
Martin318is said:
Why so expensive? The basic unit is 630 euro.....

840 Euro for the cheapest model on the website.

930 Euro for the SRAM which is NZ$1550. Not sure what freight is from Europe but that is the issue in NZ. We have to buy in such small numbers so prices are not that favourable. If you buy from Europe the expectation I would be expect if any issues you have to go back to them. Part of the deal for bikecycle.co.nz to get the agency was having someone who actually understands racing and training with a power meter (yours truly) rather than having to send emails to Germany to get information.

That being said my Powertap s**t itself and I was without it for 8 weeks while I had to send the hub to the US. They did replace it even though it was out of warranty and I had brought it 2nd hand which was pretty awesome.

Looks like Powertap are gearing up to respond to the Garmin pedal based meter by introducing a newer Powertap that is cheaper and easier to service. Including a hearty rate strap that can estimate power (needs to be calibrated with a power meter).
 
Mar 26, 2009
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CoachFergie said:
Did a MAP test today and the P2M read 8 watts lower for max min power than my Powertap. Will use a known weight to manually test the calibration of both and my flatmates wired SRM as he thinks his is reading too high. I should be so lucky.

Im not a coach, but isn't important on a powermeter that the data showed are costant than actual real value?
I mean, your powermeter could show 8 watts lower than the real power you generated, but it doesnt matter as long as it keep showing that x watts at that x effort.

Hope I explained myself as english isnt my first language.
 
That is correct. Risky business anyway to compare power data with others.

I did a comparison of 6 power files from the road race on the weekend and the only useful comparisons are things like intensity and time spent in different power, cadence and heart rate zones.

Power is affected by so many things that the only person you can really compare with is yourself.

So yes, as long as it is consistently inaccurate you will be able to measure your own improvements.

When I initially tested the P2M cranks I used the rings off my FSA cranks and had to use an old Truvative inner ring. Having put some SRAM rings on the SRAM version of the PSM crank the "noise" we were experiencing died down considerably.

It's no Quarg, SRM or Powertap but offers a value entry level power meter for all but the Elite or those who want the greatest precision in their measurement.
 
Michele said:
Im not a coach, but isn't important on a powermeter that the data showed are costant than actual real value?
I mean, your powermeter could show 8 watts lower than the real power you generated, but it doesnt matter as long as it keep showing that x watts at that x effort.

Hope I explained myself as english isnt my first language.
That's true, although when wanting to compare one's performance over a long time frame, i.e. many seasons (eventually you do tend to change power meters), it's good to know the data is accurate from each meter used. It also factors into other elements of using a power meter, like assessing data collected during aerodynamic field tests when you want to go back and look at previous testing results.

Also, accuracy and precision, while different things, do tend to go hand in hand with these sorts of devices. An meter that is inherently inaccurate is more likely to also suffer from precision problems (i.e. drift in readings during a training session or from day to day).