Virtual Watts: Watt Is It?



So what is 'Virtual Watts'?

You may have heard the term bandied about on club rides or at the gym: Virtual Watts. Simply put, Virtual Watts is way to calculate how much wattage you're generating while suffering without having to invest in a bona fide power meter.

It's the calculation of the speed of either your rear wheel or the flywheel of your trainer mapped against the unique power curve of your trainer (the relationship between your speed and the resistance offered by the trainer). This relationship can be a straight line (linear) or a curve (progressive) or however the manufacturer decides to design it. Each model of trainer has a unique power curve.

The Sufferfest app knows how fast you're going based upon the information transmitted by your speed sensor and knows the power curve of your specific trainer, it can make an estimate about how many watts you're generating at a given time. This estimation, known as Virtual Watts, is calculated displayed on screen to help you structure your training and maximise your Return on Suffering.

To learn more about the benefits of training with power, we suggest you read on here.



Each trainer has a unique Power Curve that is matched against required power output.  


Who should use Virtual Watts?

If you don't have a power meter but want to get smarter about training then we highly recommend setting up your bike for Virtual Watts. Knowing your virtual 4DP and setting workout targets on this will help you improve your fitness in a structured, progressive way.

Setting up you turbo trainer and bike for Virtual Watts.

To capture the speed of your rear wheel you will need to mount an ANT+ or Bluetooth speed sensor to the non-driveside chain stay of your bike and a magnet to the spokes of your rear wheel. There are many popular brands and models of speed and cadence sensors, such as those from Wahoo

Install the sensors and pair it to the app (provided you have the right ANT+/Bluetooth connectivity) 

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What else do I need to know?

Training with power works best when the power data is consistent from workout to workout. The rolling resistance is the factor that will determine this consistency. There are two key things that you can do to keep your rolling resistance consistent and your virtual power accurate over time:

  1. Keep your tyre pressure consistent. If your tyres were at 90 psi for your 4DP test, make sure your tyre pressure remains as close to 90 psi. This is done best using a pump with a pressure gauge.
  2. Keep your 'trainer pressure' consistent. Trainer pressure refers to the contact between the turbo trainer and the rear tyre. To achieve consistent trainer pressure, make sure you adjust the 'roller' equally every time you install in the bike on the trainer. 


More of a visual learner? Check out this video for step-by-step instructions. 


Using Virtual Power with The Sufferfest App from The Sufferfest on Vimeo.


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