So why should a cyclist measure power?
A runner could measure performance by perceived effort or heart rate. Runners use stopwatches because they give a quantified, objective measure of performance. Cyclists have used perceived effort, heart rate, and time as performance measures, but such measures are subject to variability due to wind, slope, and air density. Power is the appropriate performance measure for cyclists. Power measurement for cyclists has recently become affordable and practical.
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Parameters
| |
Ride Data |
View Data |
|
| Max Power |
750. |
431. |
watts |
| Ave Power |
197. |
271. |
watts |
| Max Torque |
500. |
123. |
in-lbf |
| Ave Torque |
72. |
77. |
in-lbf |
| Max Speed |
48.7 |
44.1 |
kph |
| Ave Speed |
32.6 |
40.4 |
kph |
| Max Cadence |
138. |
114. |
rpm |
| Ave Cadence |
89. |
98. |
rpm |
| Max Heart Rate |
178. |
169. |
bpm |
| Ave Heart Rate |
141. |
158. |
bpm |
| Distance |
79.060 |
5.395 |
kilometers |
| |
79060. |
5395. |
meters |
| |
49.017 |
3.345 |
miles |
| |
86461. |
5900. |
yards |
| Energy |
1719.62 |
130.37 |
kJ |
| Time |
145.5 |
8.0 |
minutes |
| |
8729. |
481. |
seconds |
| |
2.425 |
0.134 |
hours |
| |
2:25:29 |
0:08:1 3 |
hh:mm:ss |
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Sample Plot and Statistics Table
The sample plot and data show power data for a short time trial done in the middle of a ride. Notice the variability in power. The course was flat. There was a tailwind of about 5 mph.
The data table shows statistics for the entire ride as well as for the current view of the data.
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What's commonly done with power measurement data?
Manufacturer's usually offer devices for transferring power measurements from the bike to a computer for plotting the data and calculating statistics. Our objective is to take this another step and offer many different analyses. We don't intend to replace the desktop analysis programs. They are the best choice for managing your data.
By offering power measurement analysis through a web interface, anyone can do the analysis, just e-mail them the data file.
Upload and Plot
To do an analysis, upload a file for processing. This could be a file on your desktop that is available to your browser. Once uploaded, you can perform analysis on it without having to upload it again. This requires that cookies be enabled in your browser. Otherwise repeated analyses will require repeated file uploads. Files will continue to be available until your browser session has been inactive for some number of minutes.
- If you want to compare two data files, open two browser windows, one showing each data file.
- You can work with Power-Tap and SRM files. SRM files must be in SRM's "as .txt format". The software will automatically distinguish between Power-Tap and SRM files.
- Plot data as a function of distance (miles, kilometers, yards, or meters) or of time (hours, minutes, or seconds).
- Select units for speed (mph, kph, or mps).
- Select a range for plotting.
- Select a Smoothing number, r. This applies a moving-average function to the data, averaging r data values for each point. Be aware that this reduces the number of data values available for plotting by r-1. The value for r must be less than or equal to 10. If the increment of time in your data is one second, this would result in a moving average over 10 data values or 10 seconds; if two seconds, a moving average over 20 seconds.
Comparison of Power-Tap, SRM, and Polar Devices
Alan Cote (a developer of Polar's power technology) sent us an Excel file that compares data recorded simultaneously on a single ride using a Power-Tap, an SRM, and a Polar power measurement device. Power as measured by all three devices is in good agreement. Polar_SRM_PowerTap_by_Myerson_6-6-02.xls (1.44MB)
© 2002 Tom Compton
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