The Powermeter Thread

Apr 21, 2009
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As I have done for uncoupled cranks I thought I would start a power meter thread to discuss the science and practice behind this measurement tool.

My Masters degree research project will be testing racing and training with a power meter against lab based power meter tests. (edit: this research has been done and my research will look at different approaches for analysing field based data recorded by a power meter).



Now just because I trained with two power meters today I didn't go twice as fast:D
 
Apr 21, 2009
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Feel free to post questions. I have used most brands of power meter or have riders I coach who have used them.

I have one question. Does anyone have some pictures of how they fitted the wiring kit on a Pinarello (FP3 to be precise)?
 
Nov 25, 2010
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I'm interested in learning about the research project, specifically what procedures and testing will be done. Also very important is knowing 'what question is intended to be answered', i.e. what is the goal of the project.

Part of doing a good 'educational research project' is to pick an interesting question that can be answered (or at least gain worthwhile info about), and actually being able to do suitable & reliable testing within the confines of budget, time, skill, etc.

Jay Kosta
Endwell NY USA
 
Sep 23, 2010
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CoachFergie said:
As I have done for uncoupled cranks I thought I would start a power meter thread to discuss the science behind this measurement tool.

My Masters degree research project will be testing racing and training with a power meter against lab based power meter tests.
Then, I guess you already know from your literature review that all of the work so far done on this subject (at least of which I am aware) show there is no benefit to the athlete to using a power meter for training or racing.

Or, if it can ever be shown that there is a benefit then it would be nice to know how much accuracy is necessary to see that benefit.
 
Sep 23, 2010
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CoachFergie said:
Feel free to post questions. I have used most brands of power meter or have riders I coach who have used them.

I have one question. Does anyone have some pictures of how they fitted the wiring kit on a Pinarello (FP3 to be precise)?
Fergie, what does this have to do with the topic of discussing the science of power meters?
 
Apr 21, 2009
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Part of owning a power meter is knowing how to set one up.

Very appropriate for "the Power Meter thread".

Part of any testing procedure is ensuring the measurement equipment is set up right.
 
Sep 23, 2010
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CoachFergie said:
Part of owning a power meter is knowing how to set one up.

Very appropriate for "the Power Meter thread".

Part of any testing procedure is ensuring the measurement equipment is set up right.
I guess if that ever came up you could provide your expertise but here was the intent of the person who started this thread
I would start a power meter thread to discuss the science behind this measurement tool.
Your post is and was off topic
 
Apr 21, 2009
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FrankDay said:
I guess if that ever came up you could provide your expertise but here was the intent of the person who started this threadYour post is and was off topic
I started the thread and beg to differ. Do let me know if I start telling lies, spamming and presenting anecdotes as evidence.
 
Sep 23, 2010
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CoachFergie said:
I started the thread and beg to differ. Do let me know if I start telling lies, spamming and presenting anecdotes as evidence.
Wake me up when you (or anyone) gets to the science part.
 
Mar 18, 2009
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FrankDay said:
Then, I guess you already know from your literature review that all of the work so far done on this subject (at least of which I am aware) show there is no benefit to the athlete to using a power meter for training or racing.
Oh, brother. Science versus Frank Day's broscience.

Take the definision of "broscience" [The predominant brand of reasoning in bodybuilding circles where the anecdotal reports of jacked dudes are considered more credible than scientific research.] and tell me it does not bear a striking resemblence to Frank Day's snake oil sales technique. Day goes one better than bro science by claiming that he's not aware of any scientific research that would contradict his ridiculous anecdote driven reasoning. At least the bros can honestly play stupid.
 
Sep 23, 2010
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BroDeal said:
Oh, brother. Science versus Frank Day's broscience.

Take the definision of "broscience" [The predominant brand of reasoning in bodybuilding circles where the anecdotal reports of jacked dudes are considered more credible than scientific research.] and tell me it does not bear a striking resemblence to Frank Day's snake oil sales technique. Day goes one better than bro science by claiming that he's not aware of any scientific research that would contradict his ridiculous anecdote driven reasoning. At least the bros can honestly play stupid.
Well, when Fergie started the PowerCranks thread all he did was post all of the studies he could find related to the subject. So far, not a one, even though there are some. here is one I know of
EFFECTS OF HIGH INTENSITY TRAINING BY HEART RATE OR POWER IN RECREATIONAL CYCLISTS

Michael E. Robinson1,2, Jeff Plasschaert2 and Nkaku R. Kisaalita1

1Center for Pain Research and Behavioral Health, University of Florida, 2Shands Sport Performance Center at University of Florida Orthopaedics and Sports Medicine Institute, USA

© Journal of Sports Science and Medicine (2011) 10, 498 - 501
ABSTRACT
Technological advances in interval training for cyclists have led to the development of both heart rate (HR) monitors and powermeters (PM). Despite the growing popularity of PM use, the superiority of PM-based training has not been established. The aim of the present study was to investigate the relative effectiveness of HR-based versus PM-based interval training on 20 km time trial (20km TT), lactate threshold (LT) power, and peak aerobic capacity (VO2max) in recreational cyclists. Participants (n =20; M age=33.9, SD =13) completed a baseline 20km TT to establish their VO2max and LT and were then randomly assigned to either HR-determined or PM-determined training sessions. Over a period of up to 5 weeks participants completed 7.2 (± 1.1) interval training sessions at their specific LT for their respective interval training method. Repeated measures analyses of variances (ANOVAs) showed that both HR-based and PM-based training groups significantly improved their LT power (F(1,16) = 28., p < 0.01, eta2 = 0.63) and 20km TT time (F(1,16) = 4.92, p = 0.04, eta2 = 0.24) at posttest, showing a 17 watt increase (9.8%) and a near 3-and-a-half minute improvement (7.8%) in 20km TT completion time. There were no significant group (HR vs. PM) x time (baseline vs. posttest) interactions for 20km TT completion time, LT power, or VO2max ratings. Our results coincide with the literature supporting the effectiveness of interval training for endurance athletes. Furthermore, our findings indicate that there is no empirical evidence for the superiority of any single type of device in the implementation of interval training. This study indicates that there are no noticeable advantages to using PM to increase performance in the average recreational cyclist, suggesting that low cost HR monitor are equally capable as training devices.
 
Sep 23, 2010
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Here is another
Effects of high-intensity training by heart rate or power in well-trained cyclists.
Swart J, Lamberts RP, Derman W, Lambert MI.
Source

Department of Human Biology, Faculty of Health Sciences, UCT/MRC Research Unit for Exercise Science and Sports Medicine, University of Cape Town, The Sport Science Institute of South Africa, Newlands, South Africa. jeroen.swart@uct.ac.za
Abstract

The aim of this study was to determine whether the performance of cyclists after 4 weeks of high-intensity training improved similarly using either heart rate or power to prescribe training. Twenty-one well-trained men cyclists (age, 32 +/- 6 years; peak power output, 371 +/- 46 W) were randomly assigned to a power-based (GPOWER) or heart rate-based (GHEART) high-intensity training (HIT) group or a control group (GCONTROL). Training consisted of 8 repetitions of 4 minutes at either 80% of peak power output (GPOWER) or at the heart rate coinciding with 80% of peak power output (GHEART), with rest periods of 90 seconds. A 40-km time trial and VO2max test were performed before and after 8 training sessions. There were significant improvements (p < 0.05) in peak power output (GPOWER = 3.5%; GHEART = 5.0%) and 40-km time trial performance (GPOWER = 2.3%; GHEART = 2.1%) for both of the high-intensity groups. Although there were no significant differences between groups for these variables, when the data were analyzed using magnitude-based effects, the GHEART group showed greater probability of a "beneficial" effect for peak power output. The current general perception that prescribing training based only on power is more effective than prescribing training based on heart rate was not supported by the data from this study. Coaches who are unable to monitor progress frequently should prescribe training based on heart rate, when intervals are performed under stable conditions, because this may provide an additional advantage over prescribing training using power.
This study has also been discussed here.

If there are any other scientific studies on the subject I am not aware of them and no one arguing for the benefits of a power meter has ever made reference to one.
 
Apr 21, 2009
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Sports Engineering (2005) 8, 137–144

A static method for obtaining a calibration factor for
SRM bicycle power cranks

Andrea L. Wooles, Anthony J. Robinson and Peter S. Keen
Great Britain Cycling Team, National Cycling Centre, Manchester, UK

Abstract

Many scientists and coaches are interested in mechanical power produced during cycling, and
use Schoberer Rad Meßtechnik (SRM) bicycle power cranks to obtain this data. However, it has
been expensive and difficult to calibrate SRM cranks, causing much of the collected data to be
unreliable. We present a static method, derived from first principles, for obtaining a calibration
factor for SRM cranks.

A known mass and lever arm (chainring of a known diameter) are used to apply a known
torque load to the instrument in four positions, and the output frequencies are used to calculate
the calibration factor in Hz/N m. The reproducibility of this method is ±0.01 Hz/Nm, which is
acceptable for the application of the instrument, which is measurement of mechanical power
application by cyclists at the crank.

The method is reliable, inexpensive, and easy to set up, and will allow higher confidence in
data collected using SRM power cranks. We recommend calibration of the power meter once
every six months because of the measured drift of the calibration factor over time.

Keywords: cycling, mechanical power, ergometry, reproducibility
 
Apr 21, 2009
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Accuracy of SRM and Power Tap Power
Monitoring Systems for Bicycling

ANDREW S. GARDNER1,2, SHAUN STEPHENS3, DAVID T. MARTIN1, EVAN LAWTON1,
HAMILTON LEE1, and DAVID JENKINS2
1Department of Physiology, Australian Institute of Sport, AUSTRALIA; 2School of Human Movement Studies, The
University of Queensland, AUSTRALIA; and 3Triathlon Program, Queensland Academy of Sport, AUSTRALIA

ABSTRACT
GARDNER, A. S., S. STEPHENS, D. T. MARTIN, E. LAWTON, H. LEE, and D. JENKINS. Accuracy of SRM and Power Tap Power
Monitoring Systems for Bicycling. Med. Sci. Sports Exerc., Vol. 36, No. 7, pp. 1252–1258, 2004. Purpose: Although manufacturers
of bicycle power monitoring devices SRM and Power Tap (PT) claim accuracy to within 2.5%, there are limited scientific data available
in support. The purpose of this investigation was to assess the accuracy of SRM and PT under different conditions. Methods: First,
19 SRM were calibrated, raced for 11 months, and retested using a dynamic CALRIG (50–1000Wat 100 rpm). Second, using the same
procedure, five PT were repeat tested on alternate days. Third, the most accurate SRM and PT were tested for the influence of cadence
(60, 80, 100, 120 rpm), temperature (8 and 21°C) and time (1 h at 300 W) on accuracy. Finally, the same SRM and PT were
downloaded and compared after random cadence and gear surges using the CALRIG and on a training ride. Results: The mean error
scores for SRM and PT factory calibration over a range of 50–1000 W were 2.3  4.9% and 2.5  0.5%, respectively. A second
set of trials provided stable results for 15 calibrated SRM after 11 months (0.8  1.7%), and follow-up testing of all PT units
confirmed these findings (2.7  0.1%). Accuracy for SRM and PT was not largely influenced by time and cadence; however, power
output readings were noticeably influenced by temperature (5.2% for SRM and 8.4% for PT). During field trials, SRM average and
max power were 4.8% and 7.3% lower, respectively, compared with PT. Conclusions: When operated according to manufacturers
instructions, both SRM and PT offer the coach, athlete, and sport scientist the ability to accurately monitor power output in the lab and
the field. Calibration procedures matching performance tests (duration, power, cadence, and temperature) are, however, advised as the
error associated with each unit may vary. Key Words: CALIBRATION, CYCLING, ERGOMETERS, VALIDITY
 
Apr 21, 2009
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Nimmerichter, Alfred , Eston, Roger G. , Bachl, Norbert and Williams, Craig(2011) 'Longitudinal
monitoring of power output and heart rate profiles in elite cyclists', Journal of Sports Sciences, 29: 8, 831 — 839

Abstract
Power output and heart rate were monitored for 11 months in one female (V O2max: 71.5 mL  kg71  min71) and ten male
(V O2max: 66.5+7.1 mL  kg71  min71) cyclists using SRM power-meters to quantify power output and heart rate
distributions in an attempt to assess exercise intensity and to relate training variables to performance. In total, 1802 data sets
were divided into workout categories according to training goals, and power output and heart rate intensity zones were
calculated. The ratio of mean power output to respiratory compensation point power output was calculated as an intensity
factor for each training session and for each interval during the training sessions. Variability of power output was calculated
as a coefficient of variation. There was no difference in the distribution of power output and heart rate for the total season
(P<0.15). Significant differences were observed during high-intensity workouts (P<0.001). Performance improvements
across the season were related to low-cadence strength workouts (P<0.05). The intensity factor for intervals was related to
performance (P<0.01). The variability in power output was inversely associated with performance (P<0.01). Better
performance by cyclists was characterized by lower variability in power output and higher exercise intensities during
intervals.
Keywords: Oxygen consumption, anaerobic threshold, athletic performance, cycling, mobile power meter
 
Apr 21, 2009
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Both the Swart and Robinson papers show us that doing the same interval session with a HR monitor and a power meter leads to no difference in performance on a fitness test. Might have well compared the difference between doing the same interval programme and watching Family Guy verses The Simpsons.
 
Apr 21, 2009
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Measuring Changes in Aerodynamic/Rolling
Resistances by Cycle-Mounted Power Meters

ALLEN C. LIM, ERIC P. HOMESTEAD, ANDREW G. EDWARDS, TODD C. CARVER, RODGER KRAM,
and WILLIAM C. BYRNES

Department of Integrative Physiology, University of Colorado, Boulder, CO

ABSTRACT
LIM, A. C., E. P. HOMESTEAD, A. G. EDWARDS, T. C. CARVER, R. KRAM, and W. C. BYRNES. Measuring Changes in
Aerodynamic/Rolling Resistances by Cycle-Mounted Power Meters. Med. Sci. Sports Exerc., Vol. 43, No. 5, pp. 853–860, 2011.
Purpose: To develop a protocol for isolating changes in aerodynamic and rolling resistances from field-based measures of power
and velocity during level bicycling. Methods: We assessed the effect of body position (hands on brake hoods vs drops) and tire
pressure changes (414 vs 828 kPa) on aerodynamic and rolling resistances by measuring the power (Pext)-versus-speed (V ) relationship
using commercially available bicycle-mounted power meters. Measurements were obtained using standard road bicycles in
calm wind (G1.0 mIsj1) conditions at constant velocities (acceleration G0.5 mIsj2) on a flat 200-m section of a smooth asphalt road.
For each experimental condition, experienced road cyclists rode in 50-W increments from 100 to 300 W for women (n = 2) or 100 to
400 W for men (n = 6). Aerodynamic resistance per velocity squared (k) was calculated as the slope of a linear plot of tractive
resistance (RT = power/velocity) versus velocity squared. Rolling resistance (Rr) was calculated as the intercept of this relationship.
Results: Aerodynamic resistance per velocity squared (k) was significantly greater (P G 0.05) while riding on the brake hoods compared
with the drops (mean T SD: 0.175 T 0.025 vs 0.155 T 0.03 NIVj2). Rolling resistance was significantly greater at 60 psi
compared with 120 psi (5.575 T 0.695 vs 4.215 T 0.815 N). Conclusions: These results demonstrate that commercially available power
meters are sensitive enough to independently detect the changes in aerodynamic and rolling resistances associated with modest changes
in body position and substantial changes in tire pressure. Key Words: DRAG COEFFICIENT, POWER TAP, SRM, TESTING
 
power Tap and Q rings

Fergie,
Thanks for starting a thread that can answer some Power Meter questions. I have a PowerTap hub and my cranks are Rotor 3D+ with Q rings. I have been riding them for three years and like them. I have no proof that they have increased my power at all but like the feel of them from the first time I rode them. My question is calibration, would this be done differently because of the Q rings. thanks

Rob
 
Nov 25, 2010
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Coach Fergie,

When designing your project, I suggest that you be very careful and critical to avoid 'problem areas' such as were discussed regarding the Burns article.

For example -

The length / intensity / frequency of the training period needs to be adequate to produce results that are measureable.

If the testers are told/requested to DO something, then there should be some method to objectively verify that it was done, and how well it was done.

If the testers are being taught a 'new technique', then there should be some testing to determine what is their 'current technique'. So that before-after comparisons are meaningful.

I don't know what you have in mind to study, but I would like to see a study that compares training by -
1) power meter
2) heart rate
3) perceived exertion

Jay Kosta
Endwell NY USA
 
Sep 23, 2010
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JayKosta said:
Coach Fergie,

When designing your project, I suggest that you be very careful and critical to avoid 'problem areas' such as were discussed regarding the Burns article.

For example -

The length / intensity / frequency of the training period needs to be adequate to produce results that are measureable.

If the testers are told/requested to DO something, then there should be some method to objectively verify that it was done, and how well it was done.

If the testers are being taught a 'new technique', then there should be some testing to determine what is their 'current technique'. So that before-after comparisons are meaningful.

I don't know what you have in mind to study, but I would like to see a study that compares training by -
1) power meter
2) heart rate
3) perceived exertion

Jay Kosta
Endwell NY USA
Perhaps Fergie will post his ideas for a study here for critical review by the group before he finalizes his proposal. Fergie is about to find out how difficult it is to design and complete a well-designed study on a subject such as this. I wonder if his own study shows no benefit to a power meter (and no other study has yet to show a benefit) if he will change his recommendations to his athletes and everyone else? This should be interesting.
 
Apr 21, 2009
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veganrob said:
Fergie,
Thanks for starting a thread that can answer some Power Meter questions. I have a PowerTap hub and my cranks are Rotor 3D+ with Q rings. I have been riding them for three years and like them. I have no proof that they have increased my power at all but like the feel of them from the first time I rode them. My question is calibration, would this be done differently because of the Q rings. thanks
You can check the calibration of a Powertap but you can't change the calibration of one.

Any engineers care to comment about hanging a known weight off a crank with a Q ring to check the calibration of a Powertap.
 
Apr 21, 2009
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FrankDay said:
Perhaps Fergie will post his ideas for a study here for critical review by the group before he finalizes his proposal. Fergie is about to find out how difficult it is to design and complete a well-designed study on a subject such as this. I wonder if his own study shows no benefit to a power meter (and no other study has yet to show a benefit) if he will change his recommendations to his athletes and everyone else? This should be interesting.
I already know how hard it is to design a study and currently the hurdles involved at the Ethics approval stage.

Frank, you still try and create a strawman by suggesting that a Power Meter should provide a benefit. A set of scales provides no benefit to the weight loss process only tells you if it is actually happening. A heart rate monitor doesn't tell you if you are fitter or not not (heart rate for a given effort can go down as you become more efficient but can also rise as you learn to tolerate a higher intensity for that duration.

I don't expect my new SRM (well second hand as I don't consider myself worthy of the latest model) to benefit my performance one bit. I do expect it to measure watts.

I performed a test of various shoes using a Powertap and initially found a difference in one brand that you would have expected but when I tested in reverse order found the opposite. I assume the difference was in the heat of the roller on the wind trainer I used. When I tested again with the SRM the difference I found was minimal and well within the margin of error you would expect in that model of SRM.

If I was being funded to perform the tests I would use the erg at the local Uni that has a higher sampling rate and a lower margin of error.
 
Sep 23, 2010
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CoachFergie said:
You can check the calibration of a Powertap but you can't change the calibration of one.

Any engineers care to comment about hanging a known weight off a crank with a Q ring to check the calibration of a Powertap.
Just as the calibration of the powertap doesn't change with the size of the wheel or whether the bike is in the small or large chain ring the fact that one has a non-round chain ring has no effect on the calibration or accuracy of the powertap.
 
Apr 21, 2009
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JayKosta said:
When designing your project, I suggest that you be very careful and critical to avoid 'problem areas' such as were discussed regarding the Burns article.

For example -

The length / intensity / frequency of the training period needs to be adequate to produce results that are measureable.

If the testers are told/requested to DO something, then there should be some method to objectively verify that it was done, and how well it was done.

If the testers are being taught a 'new technique', then there should be some testing to determine what is their 'current technique'. So that before-after comparisons are meaningful.

I don't know what you have in mind to study, but I would like to see a study that compares training by -
1) power meter
2) heart rate
3) perceived exertion
Thanks for your interest Jay

My study is a methodological one looking to see if a power meter offer a reliable way of tracking changes in cycling specific fitness over time based on racing and training data compared to power meter data from a lab based test.

I am open to suggestions of doing a study that does compare those three variables but how would you get beyond the issues of the Swart and Robinson papers where each group essentially performs the same training. No surprise that there was no significant change in performance in the heart rate and power meter groups.

One question I would like to test is whether a power meter improves pacing of events like the 40km TT. I have some riders who sit on a power number while others prefer to go by feel. Then it would also depend on the course and the weather conditions for any given day.
 

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