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The Powermeter Thread

Moderator: King Boonen

05 Mar 2013 16:58

Alex Simmons/RST wrote:The issue Frank is that the common means for users to validate their power meter's calibration themselves is to use the static torque check method, which involves applying a known torque to the meter and comparing that known torque to the reading provided by the power meter.

Typically this is done by hanging a precisely known weight from the pedal spindle of a horizontal crank arm as that's usually most convenient/not all that difficult to do. Known mass + known length of crank = known torque applied.

However when using this method for checking a Powertap, since the measured torque is applied to the crank and not the hub, then you also need to include the chainring and cog sizes in the calculation of what torque is "felt" at the rear hub.

Hence, what should one do when using a chainring with variable effective ring size?

The way around this problem for a Powertap user with non-round rings is not to use the crank to apply the torque, but apply the torque to the wheel via another method that is not transmitted via the drivetrain.

e.g. you could hang a known mass from the edge of the wheel - all you then need to know is the radius from centre of wheel axle to the point you are hanging the mass (and the mass of course) and to make sure the point at which the mass is being applied forms a horizontal line with the wheel axle. Slowly rotating the wheel when near horizontal will help find this point.

Another means would be to use a hanging weight scale fixed at one end connected via rope to the outer edge of the rear wheel from the other end so that the "rope" forms a tangent to the wheel and then use a rope ratchet to apply some tension. The scale will then give you the equivalent "weight" of the force being applied, multiplied by the radius to the point of attachment to the wheel and that's the known hub torque you can use to compare with what the Powertap reports.

Or, as I pointed out, would be to change to a round chain ring for this purpose.
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FrankDay
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05 Mar 2013 17:01

acoggan wrote:Ask Bradley Wiggins.
Has he written a scientific paper on the subject? Or, would I get an anecdotal report?
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05 Mar 2013 17:14

elapid wrote:Frank - I'm not sure if you don't get it or are deliberately being obtuse, but please let this be a discussion about power meters and please do not let it degenerate into the farce that is the multitude of crank/pedalling threads.
OK, I will stay on topic

Power meters do not improve performance
. They are a measuring device, just the same as a heart rate monitor and anything else that measures data. However, there are many advantages for using a power meter to measure data compared to a heart rate monitor because it is a more accurate reflection of your work at that time regardless of road and weather conditions. In a training situation, it can allow you to quantify improvements over a given course. In a race situation, it can help you pace yourself so that you don't blow up.
If power meters do not improve performance where exactly are those advantages for the competitive athlete. The ability to better quantify data without improving performance seems to me like that is only an advantage for the obsessive compulsive data freak and no-one else.

Andrew Coggan's books on power meters and their use are excellent resources. I presume you have read them, but if not I would definitely recommend them.
I understand Dr. Coggan has written a book on the subject but when asked he is unable to supply a single paper that supports any advantage for the power meter over other tools or methods. All his book does, as far as I can tell, is take some known training principles and apply them using the power meter as an effort feedback device as opposed to other effort feedback methods. Just because people get a reproducible number from the device is not evidence that the racing outcome from using it is superior.
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FrankDay
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05 Mar 2013 17:35

FrankDay wrote:OK, I will stay on topicIf power meters do not improve performance where exactly are those advantages for the competitive athlete. The ability to better quantify data without improving performance seems to me like that is only an advantage for the obsessive compulsive data freak and no-one else.I understand Dr. Coggan has written a book on the subject but when asked he is unable to supply a single paper that supports any advantage for the power meter over other tools or methods. All his book does, as far as I can tell, is take some known training principles and apply them using the power meter as an effort feedback device as opposed to other effort feedback methods. Just because people get a reproducible number from the device is not evidence that the racing outcome from using it is superior.


I am self-confessed data freak. I cycle for fun and no longer race. That being said, I own two PT wheels and train with power. Personally, these are the advantages I see in using a power meter:

- Quantify improvements in training. If you are training towards a specific goal, then you can measure spatial improvements in power output over that time period and this measurement is not affected by external influences (e.g., my power output will not be affected by wind conditions, but my speed will be slower and HR higher if I am doing this test into a headwind). For instance, measuring my average power output over the same course for a 20min TT.

- Train better in specific situations. The response of HR to increased work is delayed. If you are doing longer intervals, this delay probably has no effect. However, if you are doing sprint intervals then this delay is problematic and the information you get from a power meter is much more accurate.

- Reproducibility. I think this is important when used correctly, but to be honest probably only benefits professionals.

- Racing. If you know your functional threshold and what you can and cannot do, then you can gauge your work level to make sure you do not red line and bomb out.

Bottom line, a power meter is just a training tool. It is more reliable and more accurate than a heart rate monitor, but it is still just a training tool. You could take your argument an additional step and argue that no measuring device actually provides an improvement in performance. Have studies been done to prove that training with and without a heart rate monitor make a difference to performance? I doubt it. Does it matter if you do interval training with a heart rate monitor, a power meter, or nothing? Probably not, just as long as you're doing interval training.
"If you're going through hell, keep going." - Winston Churchill
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05 Mar 2013 17:57

FrankDay wrote:Has he written a scientific paper on the subject? Or, would I get an anecdotal report?


You're a hypocrite, Frank.
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05 Mar 2013 17:59

FrankDay wrote:I understand Dr. Coggan has written a book on the subject but when asked he is unable to supply a single paper that supports any advantage for the power meter over other tools or methods.


Science isn't always the best way of answering some questions. (That's especially true when the people asking the questions, and those doing the studies, clearly don't understand the scientific process.)
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05 Mar 2013 18:47

FrankDay wrote:The ability to better quantify data without improving performance seems to me like that is only an advantage for the obsessive compulsive data freak and no-one else.


More trolling.
Hamish Ferguson
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05 Mar 2013 18:51

Power output during women’s World Cup road cycle racing

Tammie R. Ebert David T. Martin
Warren McDonald James Victor
John Plummer Robert T. Withers

Eur J Appl Physiol (2005) 95: 529–536

Abstract Little information exists on the power output
demands of competitive women’s road cycle racing. The
purpose of our investigation was to document the power
output generated by elite female road cyclists who
achieved success in FLAT and HILLY World Cup races.
Power output data were collected from 27 top-20 World
Cup finishes (19 FLAT and 8 HILLY) achieved by 15
nationally ranked cyclists (mean ± SD; age: 24.1±4.0 -
years; body mass: 57.9±3.6 kg; height: 168.7±5.6 cm;
V_ O2max : 63.6±2.4 mL kg1 min1 ; peak power during
graded exercise test (GXTpeak power): 310±25 W). The
GXT determined GXTpeak power, V_ O2peak; lactate threshold
(LT) and anaerobic threshold (AT). Bicycles were
fitted withSRMpowermeters, which recorded power (W),
cadence (rpm), distance (km) and speed (km h1). Racing
data were analysed to establish time in power output and
metabolic threshold bands and maximal mean power
(MMP) over different durations. When compared to
HILLY, FLAT were raced at a similar cadence (75±8 vs.
75±4 rpm, P=0.93) but higher speed (37.6±2.6 vs.
33.9±2.7 km h1, P=0.008) and power output (192±21
vs. 169±17 W, P=0.04; 3.3±0.3 vs. 3.0±0.4 W kg1,
P=0.04). During FLAT races, riders spent significantly
more time above 500 W, while greater race time was spent
between 100 and 300 W (LT-AT) for HILLY races, with
higher MMPs for 180–300 s. Racing terrain influenced
the power output profiles of our internationally competitive
female road cyclists. These data are the first to define
the unique power output requirements associated with
placing well in both flat and hilly women’s World Cup
cycling events.
Hamish Ferguson
coachfergblog.blogspot.co.nz
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05 Mar 2013 18:54

Power Output During a Professional
Men's Road-Cycling Tour

Tammie R. Ebert, David T. Martin, Brian Stephens,
and Robert T. Withers

International Journal of Sports Physiology and Performance, 2006;1:324-335

Purpose: To quantify the power-output demands of men's road-cycling stage
racing using a direct measure of power output. Methods: Power-output data were
collected from 207 races over 6 competition years on 31 Australian national male
road cyclists. Suhjects performed a maximal graded exercise tesi in the latroratory
to determine maximum aerobic-power output, and bicycles were fitted with SRM
power meters. Races were described as flat, hilly, or criterium, and linear mixed
modeling was used to compare the races. Results: Crilerium was the shortest
race and displayed the highest mean power output (criterium 262 ± 30 v hilly
203 ± 32 V flat 188 ± 30 W), percentage total race time above 7.5 W/kg (criterium
15.5% ± 4.1% V hiUy 3.8% ± 1.7% v flat 3.5% ± 1.4%) and SD in power
output (criterium 250 v hilly 165 v flat 169 W). Approximately 67%. 80%, and
85% of total race time was spent below 5 W/kg for criterium, hilly and flat races,
respectively. About 70,40. and 20 sprints above maximum aerobic-power output
occurred during criterium, hilly, and flat races, respectively, with most sprints being 6 to
10 s. Conclusions: These data extend previous research documenting the demands of
men's road cycling. Despite the relatively low mean power output, races were
characterized by multiple high-intensity surges above maximum aerobic-power
output. These data can be used to develop sport-specific interval-training programs
that replicate the demands of competition.

Key Words: SRM power meter, terrain, criterium
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05 Mar 2013 21:15

acoggan wrote:Science isn't always the best way of answering some questions. (That's especially true when the people asking the questions, and those doing the studies, clearly don't understand the scientific process.)
??? Are there any questions related to cycling performance in which you think science would be unable to provide the best answer? What would be the first choice for better answering those questions? And, why?
Life is short, both reading my posts and training with PowerCranks will make it seem longer
FrankDay
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05 Mar 2013 21:32

elapid wrote:I am self-confessed data freak. I cycle for fun and no longer race. That being said, I own two PT wheels and train with power. Personally, these are the advantages I see in using a power meter:

- Quantify improvements in training. If you are training towards a specific goal, then you can measure spatial improvements in power output over that time period and this measurement is not affected by external influences (e.g., my power output will not be affected by wind conditions, but my speed will be slower and HR higher if I am doing this test into a headwind). For instance, measuring my average power output over the same course for a 20min TT.

Better quantification is important to the data geek. However, an argument can be made that the pm only offers easier quantification. It is not clear it is better quantification since racing is about speed and not just about power. If the rider increases power by attaining a lesser aerodynamic position he may actually go slower. Repeat time-trials over a loop course when wind conditions are light are also a way of quantifying ability. It is how it was done for years and years before power meters. While power meter data is more easily obtained there is no evidence it is better than other methods at quantifying racing improvement.

- Train better in specific situations. The response of HR to increased work is delayed. If you are doing longer intervals, this delay probably has no effect. However, if you are doing sprint intervals then this delay is problematic and the information you get from a power meter is much more accurate.
A nice hypothesis. There is no evidence to support it however.It may be true but scientific attempts to show such an advantage have failed.

- Reproducibility. I think this is important when used correctly, but to be honest probably only benefits professionals.
Another hypothetical advantage. It may be true but it has never been shown. Lots of world champions have trained and raced without power meters since the advent of them.

- Racing. If you know your functional threshold and what you can and cannot do, then you can gauge your work level to make sure you do not red line and bomb out.
Again, a hypothetical advantage that has never been actually demonstrated.

Bottom line, a power meter is just a training tool. It is more reliable and more accurate than a heart rate monitor, but it is still just a training tool. You could take your argument an additional step and argue that no measuring device actually provides an improvement in performance. Have studies been done to prove that training with and without a heart rate monitor make a difference to performance? I doubt it. Does it matter if you do interval training with a heart rate monitor, a power meter, or nothing? Probably not, just as long as you're doing interval training.
While a power meter may be more reliable and accurate at measuring power than a HRM it may be possible that the HRM is a better measure of relative stress on the body. Which is more important in racing, especially endurance racing? All of these arguments for the power meter are simply rationalizations to justify the significant expenditure that makes one look more serious because there is simply no evidence right now that use of the tool makes any difference in outcome.

And, I have made the HRM argument also. I am not aware of any evidence that using a HRM is more effective than using perceived exertion as the feedback tool. However, I only make that argument as a performance enhancement tool. I would not make that argument in the athlete with cardiovascular disease.
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FrankDay
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05 Mar 2013 21:58

FrankDay wrote:??? Are there any questions related to cycling performance in which you think science would be unable to provide the best answer? What would be the first choice for better answering those questions? And, why?


1. Yes (such as the best way for a given individual to train).

2. Empiricism guided by data gathered with a powermeter.

3A. Cost (in terms of time and $$).

3B. Recognition of the principle of individuality.
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05 Mar 2013 23:30

FrankDay wrote:Better quantification is important to the data geek.


Trolling.

However, an argument can be made that the pm only offers easier quantification. It is not clear it is better quantification since racing is about speed and not just about power.


Racing is about either crossing the line first or recording the fastest time for a given distance. I have previously given the example of Scott Molina losing an Age Group Kona title despite recording the fastest swim, bike and run splits but losing time in the transition. Also there may be faster riders who lose because they choose a poor line or as you say a more powerful rider who has bad aerodynamics.

Repeat time-trials over a loop course when wind conditions are light are also a way of quantifying ability. It is how it was done for years and years before power meters.


But now we have power meters we can see subtle differences due to changes in temperature, wind speed, wind direction, riding line, pacing while the watch only told us the time.

While power meter data is more easily obtained there is no evidence it is better than other methods at quantifying racing improvement.


There is considerable evidence. When I did my first anaerobic threshold test in 1989 watts were only used to quantify the stages or ramps in the test and heart rate and lactate were the main things monitored. Now in most performance tests reported in the literature or as used by most National or Professional Squads power is the key metric they track.

Which is more important in racing, especially endurance racing? All of these arguments for the power meter are simply rationalizations to justify the significant expenditure that makes one look more serious because there is simply no evidence right now that use of the tool makes any difference in outcome.


More trolling. It would be beyond belief that a former engineer would not know the difference between a method of improving outcomes and the equipment used to measure those outcomes.

And, I have made the HRM argument also. I am not aware of any evidence that using a HRM is more effective than using perceived exertion as the feedback tool. However, I only make that argument as a performance enhancement tool.


None (power meter, HRM or Perceived Exertion) are performance enhance tools or methods.
Hamish Ferguson
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06 Mar 2013 00:11

acoggan wrote:1. Yes (such as the best way for a given individual to train).

2. Empiricism guided by data gathered with a powermeter.

3A. Cost (in terms of time and $$).

3B. Recognition of the principle of individuality.
Well, that is nothing more than saying "trust me, I know what I am talking about".

In fact, I would submit that science should be able to answer the question as to the best way for an individual to train. It just isn't capable of doing that now. While it may be true that a power meter may be part of that answer for some individuals there is simply no scientific evidence now that even suggests that to be the case. However, we do have your opinion which, I suspect, differs from the opinion of many others. How do we know which opinion is better? That is a question science should be able to answer, albeit with some difficulty.
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FrankDay
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06 Mar 2013 00:23

FrankDay wrote:In fact, I would submit that science should be able to answer the question as to the best way for an individual to train. It just isn't capable of doing that now.


Which is ignoring 100 years of sport science. The last 20 years in particular when power is the key metric when measuring for a change in cycling specific fitness.

While it may be true that a power meter may be part of that answer for some individuals there is simply no scientific evidence now that even suggests that to be the case.


Trolling.

I have listed several papers in this thread alone that shows that a power meter does what it claims, how to calibrate a power meter and have started to list some papers showing how power is the most useful measure for determining event demands.
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06 Mar 2013 00:26

The Record Power Profile to Assess Performance in
Elite Cyclists

J. Pinot , F. Grappe

Abstract

The purpose of this study was to assess the
Record Power Profile (RPP) of cyclists, i. e., the
relationship between different record Power
Output (PO) and the corresponding durations
through a whole race season. We hypothesized
that PO of different effort durations could differ
according to the cyclist’s category and race
performance profile. 17 cyclists (9 professionals
and 8 elites) performed all trainings and competitions
during 10 months with a mobile power
meter device (SRM) mounted on their bike. The
results show that the cyclists ’ RPP is a hyperbolic
relationship between the diff erent record PO and
time durations. It significantly reflects the characteristics
of different skills: 1) sprinters have
the highest record PO within zone 5, 2) climbers
present the highest record PO within zones 2 – 3
and, 3) climbers and flat specialists have higher
zone 1 record PO than sprinters. These results
suggest that the RPP represents “ a signature ” of
the cyclists ’ physical capacity and that it allows
the determination of different training intensities.
The RPP appears as a new concept that is
interesting for coaches and scientists in order to
evaluate performance in cycling.
Hamish Ferguson
coachfergblog.blogspot.co.nz
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06 Mar 2013 00:30

The Peronnet–Thibault mathematical model applied to the record power profile in cycling

J. Pinot* and F. Grappe

In cycling, the new concept of record power profile (RPP)
allows the expression and the monitoring of the physical
potential of the cyclist through the relationship between
the different record power output (PO) and the time (Pinot
and Grappe 2010, 2011). PO developed by a cyclist is
becoming a biomechanical variable of performance, which
is measured today in routine directly on the bicycle during
training and competition. The RPP appears to be an
innovative method for the cycling training process and the
evaluation of the different physical capacities of the cyclist
(Pinot and Grappe 2010).
Hamish Ferguson
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06 Mar 2013 00:32

The ‘Power Profile’ for determining the physical
capacities of a cyclist

J. Pinot & F. Grappe

Monod and Scherrer have determined the concept of
critical power (CP) by establishing a linear relation
between the time to exhaustion (Tex) and (1) the total work
performed (Monod and Scherrer 1965) and (2) the distance
covered (Scherrer 1958). To improve this concept,
Peronnet and Thibault (1987) have suggested a more
elaborate model that describes the relationship between
the percentage of maximal aerobic velocity and the time of
exercise from 7 min to 2 h. This model allows the
evaluation of three physical capacities of an athlete: Tex,
CP and endurance. It is possible to ameliorate this model
by determining the ‘Power Profile’ (PP) of a cyclist. The
PP can assess more physical capacities (Figure 1) from the
relationship between the maximum power output (POmax)
sustained (during trainings and competitions) and the time
between 1 s and 4 h (Larrazabal et al. 2006; Villerius et al.
2007). PO developed by a cyclist becomes a biomechanical
variable of performance which is currently measured
in routine directly on the bicycle during training and
competition. For that, it is necessary to fix a powermeter
on the bike (SRM training system or Powertap). The
simplicity of use of these systems pushes the coaches and
the cyclists to use PO for the training follow-up. As the
level of PO is dependent on the exercise intensity, the
analysis of PO during all the trainings and competitions
permits the determination of the PP of the cyclist. From
there, it is possible to make PP comparisons between (1)
different cyclists according to the age and race category
and (2) during a season for a cyclist.
Hamish Ferguson
coachfergblog.blogspot.co.nz
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06 Mar 2013 00:32

CoachFergie wrote:The Record Power Profile to Assess Performance in
Elite Cyclists

J. Pinot , F. Grappe

Abstract

The purpose of this study was to assess the
Record Power Profile (RPP) of cyclists, i. e., the
relationship between different record Power
Output (PO) and the corresponding durations
through a whole race season. We hypothesized
that PO of different effort durations could differ
according to the cyclist’s category and race
performance profile. 17 cyclists (9 professionals
and 8 elites) performed all trainings and competitions
during 10 months with a mobile power
meter device (SRM) mounted on their bike. The
results show that the cyclists ’ RPP is a hyperbolic
relationship between the diff erent record PO and
time durations. It significantly reflects the characteristics
of different skills: 1) sprinters have
the highest record PO within zone 5, 2) climbers
present the highest record PO within zones 2 – 3
and, 3) climbers and flat specialists have higher
zone 1 record PO than sprinters. These results
suggest that the RPP represents “ a signature ” of
the cyclists ’ physical capacity and that it allows
the determination of different training intensities.
The RPP appears as a new concept that is
interesting for coaches and scientists in order to
evaluate performance in cycling.


Gee, now THERE'S a novel idea. :rolleyes::mad:
acoggan
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06 Mar 2013 00:34

FrankDay wrote:Well, that is nothing more than saying "trust me, I know what I am talking about".


Not me: I'm not a coach, nor have I ever pretended to be one.

FrankDay wrote:In fact, I would submit that science should be able to answer the question as to the best way for an individual to train. It just isn't capable of doing that now.


Nor is it likely to ever be able to do so (due to 3A that I previously listed).
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