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TrainerRoad VirtualPower compared to Stages Power Meter.

Thursday, March 27, 2014 by  
Filed under Daily Blog

March
27
2014

Now that I’m using a Stages power meter, I thought it would be interesting to compare its power data to TrainerRoad’s “VirtualPower” data.

Before I get to the test results, here are a few words about VirtualPower, the equipment I used for my tests and my testing methodology.

What is TrainerRoad’s “VirtualPower”?
For cyclists who wish to improve their speed and fitness, nothing is more effective than power-based training (for more information on training with power, please see my article “Coggan’s Power-Based Training“). Unfortunately power meters are not inexpensive items (although that is slowly changing), and are outside the budget of many cyclists. This is where TrainerRoad’s “VirtualPower” comes in.

Simply put, “VirtualPower” works by converting the cyclist’s speed into power using known power curves for indoor trainers that are supported by TrainerRoad (most are). VirtualPower is an inexpensive, yet accurate, alternative to expensive power meters.

 

TrainerRoad workout data displayed after completing the main test. All tests were performed in my Bike Torture Chamber.

TrainerRoad workout data displayed on laptop after completing the main test. All tests were performed in my Bike Torture Chamber.

Equipment Used
Here’s a list of the equipment I used for my tests. For more detailed information and photos of my Bike Torture Chamber (BTC), please see this article.

 

Testing Methodology
All tests were performed using the following procedures and settings:

  • Rear tire inflated to 120 PSI
  • Kurt Kinetic Road Machine rear roller set to 3.5 turns
  • Stages power meter zeroed out/calibrated immediately preceding each test
  •  

    TEST #1: 10 minute “freeride” test

    The first test I performed was a simple 10-minute “freeride” test. I used various gears, speeds and cadences. Here are the test results (click any image to enlarge):

     

    TrainerRoad's VirtualPower (Purple) compared to Stages Power Meter (Red): 10 minute test - Data Chart

    TrainerRoad’s VirtualPower (Purple) compared to Stages Power Meter (Red): 10 minute test – Data Chart

     

    TrainerRoad's VirtualPower (Purple) compared to Stages Power Meter (Red): 10 minute test - Data Summary

    TrainerRoad’s VirtualPower (Purple) compared to Stages Power Meter (Red): 10 minute test – Data Summary

     

    As you can see, the Stages starts off measuring a few watts higher than TrainerRoad’s VirtualPower, but as the rear tire heats up VirtualPower tracks nearly identically to the Stages for the rest of the ride. The final average power output was absolutely identical at 178 watts.

     

    TEST #2: 60 minute TrainerRoad workout (“Homers Nose”)

    The second test I performed was a 60-minute TrainerRoad workout. For this test, once again I used various gears, speeds and cadences, and I also included a couple of out-of-the-saddle stomps. Here are the test results (click any image to enlarge):

     

    TrainerRoad’s Virtual Power (Purple) compared to Stages Power Meter (Red): 60 minute test – Data Chart

    TrainerRoad’s Virtual Power (Purple) compared to Stages Power Meter (Red): 60 minute test – Data Chart

     

    TrainerRoad's VirtualPower (Purple) compared to Stages Power Meter (Red): 60 minute test - Data Summary

    TrainerRoad’s VirtualPower (Purple) compared to Stages Power Meter (Red): 60 minute test – Data Summary

     

    Once again, the Stages started off with higher wattage readings than TrainerRoad’s VirtualPower; however, as was the case with the shorter test, once the rear tire warmed up the two data lines pull together. The interesting thing is that after 14 minutes or so, TrainerRoad’s VirtualPower readings begin to read consistently higher than the Stages power meter.

    The final result was a 21 watt higher average power reading from TrainerRoad’s VirtualPower.

    Clearly TrainerRoad’s VirtualPower is an extremely effective way to train without investing in a power meter. Ultimately the ~21 watt difference between the two power sources is not really relevant, it’s the consistency from one workout to the next that matters. Having used TrainerRoad’s VirtualPower for more than a year now, I can confirm that the data is extremely consistent from one workout to the next, provided that care is taken to ensure that rear tire pressure and the Kinetic’s roller resistance remain identical.

    For my followup article with another test and my conclusions, please see TrainerRoad VirtualPower compared to Stages Power Meter: Round 2!

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