Is indoor trainer virtual power consistent?

Most serious cyclists would agree that the best way to gauge your indoor cycling performance is to monitor your power output through a smart trainer or a power meter.

If a smart trainer or a power meter is beyond your budget, you can install a speed sensor in the rear wheel of your bike and then use the virtual power settings on your cycling training app.

Is indoor trainer virtual power consistent? Virtual power will be able to provide consistent data as long as you keep your tire pressure and trainer pressure consistent in every workout.

Use the tire pressure setting recommended by your trainer and calibrate it at least every week.

Keeping everything the same will help you monitor your progress over time.

Why power training?

There are many ways by which you can measure the efforts in your training namely the Rate of Perceived Exertion (RPE) Scale, heart rate, and power.

Rate of Perceived Exertion is a scale from 0 -10 which is used to measure the intensity of the workout, with 0 as no intensity and 10 as the maximum intensity.

The limitation of this scale is that it is very subjective. How do you know which number to choose to indicate your intensity level?

You can use the talk test (if you are catching your breath while talking and exercising means you are doing high-intensity workout), how tired you feel, your heartbeat, sweat.

But all of the above depends on your perception and your level of fitness. So for me, it is not really the best metric for indoor cycling training.

How about using heart rate to train? I still think it is useful and much better compared to relying on RPE alone. However, it still has its limitations.

Sometimes your resting and maximum heart rate can be affected by stress, illness, medication, fatigue, or some other factors. Thus your target heart rate could be off. (But then again, if you are feeling particularly ill, I advise you to take a rest than pressure yourself to workout.)

Personally, I still use a heart rate monitor when training but in conjunction with a power meter.

Unlike the Rate of Perceived Exertion and heart rate, power is absolute and is not dependent on how you are feeling on a particular day.

Measured in watts, power shows how much work you have done over time, or specifically, how hard and how fast you are pushing the pedals.

Also, power is not affected by any variables, like your physical fitness, or in the case of outdoor biking, the terrain, headwinds, and other factors.

Thus many cyclists agree that it is the best metric you can use when training.

What is virtual power?

The best way to measure your power is through a smart trainer or a power meter. However, smart trainers and power meters can be pricey.

It’s a good thing that most cycling training apps like Zwift, TrainerRoad, SufferFest, and Rouvy will give you the option to use virtual power if you do not have a smart trainer or a power meter.

These apps calculate your estimated power using the speed reading from your speed sensor and the make of the trainer you have.

It is important that you input the correct model of your trainer to get fairly accurate readings. Zwift and other indoor cycling apps have tested their supported trainers to be able to calculate the watts based on the speed.

Note that the readings that you get from the virtual power may not be as accurate as from a smart trainer or a power meter but a good approximate.

That said, when you keep everything consistent (bike, tire pressure, trainer pressure, etc) you will still get data that will be useful in tracking your progress over time.

How to pair your speed sensor to your app and set up virtual power?

Before your app can provide you with the power readings, you must first pair your sensor with your device and your app.

Choose a speed sensor that has a wireless capability which means it can transmit data to a device without the use of cables. Speed sensors can either have ANT+ or Bluetooth-enabled or both.

If your sensor broadcasts only ANT+ and your phone or device only have Bluetooth capability, you will need a dongle or bridge which will allow your device to receive ANT+ signals.

Setting up virtual power in Zwift

  1. Enable Bluetooth on your device or plug in your ANT+ dongle. You may need to download and install drivers for your laptop or computer beforehand to be able to use ANT+
  2. Log into your Zwift account in your mobile or your computer.
  3. Wake up your sensor by spinning the rear wheel of your bike.
  4. On the Zwift dashboard, select the speed sensor icon and the app will automatically search and pair with speed sensor on your bike.
  5. Select the brand and model of your trainer from the list of supported trainers. If your trainer is not supported, you can choose the Not Listed option. However, Zwift cannot guarantee accurate power readings from such.

Setting up virtual power in TrainerRoad

  1. Enable Bluetooth on your device or plug in your ANT+ dongle.
  2. Open the TrainerRoad app and go to devices.
  3. Wake up your sensor by spinning the rear wheel of your bike.
  4. The app will search for a nearby device. Once it appears on your screen, tap the gray checkmark to the right.
  5. The checkmark will turn green to indicate that the device is already paired.
  6. Enable the virtual power checkbox.
  7. Select the manufacturer and model of your indoor trainer.

Setting up virtual power in The SufferFest

  1. Enable Bluetooth on your device or plug in your ANT+ dongle.
  2. Open the SufferFest app and choose the training mode you want and press play.
  3. On the next screen, tap the power icon and then turn on the “estimate power switch”.
  4. Select the brand and model of your indoor trainer.
  5. The app will automatically search for an active speed sensor and will show this on the screen.

Summary

Power-based training is preferred by most professional cyclists because it is an objective way of assessing your performance and tracking your progress.

You can still use power-based training even without a smart trainer or a power meter by using the virtual power settings of your training app and a speed and cadence sensor.

When using virtual power settings, ensure that you select the correct brand and model of your trainer.

It is important to keep your bike, tire pressure, and roller trainer pressure consistent so that you can be sure to get consistent and reliable data from the virtual power settings on your favorite training app.

Related questions?

Can I use regular road tire on my trainer? It is best to use a trainer-specific tire to avoid wear and tear of your road tire and also to reduce the noise from your trainer.

What is Functional Threshold Power? FTP is the highest average power you can sustain in an hour. Cyclists use this to determine their training zones.

Are indoor training apps free? Most indoor training apps require a monthly subscription. There are some less popular free indoor training apps like the Maximum Trainer which also lets you train using virtual power.

Adam Johnson

As a middle-aged, 40 something cyclist, my riding goals have changed over the years. A lover of all things retro, and an avid flat bar cyclist, I continue to live in the glory days of past triathlon glories.

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