Activities that are performed indoors can be marked as a Stationary Trainer or Treadmill on the Strava website.
Since the Strava mobile app cannot record stationary or indoor data without a GPS signal, these activity options are only available on the website. To mark as a Stationary Trainer or Treadmill, use the pencil icon on the activity to edit, then select the tag. You can also edit activities quickly from the My Activities page under the Training tab.
How to record and upload a stationary, indoor or treadmill activity:
Indoor activities can be recorded with any Strava-compatible GPS device or non-GPS device as long as the data recorded is compatible with the Strava uploader (or can be synced from another app to Strava). For compatible GPS devices, disabling the GPS signal when recording indoors can make it easier for Strava to analyze your data once uploaded.
If GPS data is recorded on the activity, the map will be removed when marked as a stationary trainer or treadmill. Indoor activities are usually not eligible for Strava Challenges and Club Leaderboards.
Overview of the indoor activity page:
The Stationary activity page looks like any other activity detail page but without the map. Instead, the performance graph is highlighted to give you a view of your heart rate, speed, cadence or power data if available.
If you have this accessory data, you will also be able to view Premium features such as heart rate zone breakdown and power analysis. If you don't have any accessory data, then there may not be a performance graph but you will still get credit for your elapsed time.
Activities from Virtual Trainers:
Virtual trainer activities done on software such as Zwift, BKOOL, Tacx, and others have simulated speeds and segment times. Because of this, the activities need to be categorized under the Virtual Ride activity type, or marked as private, so that the simulated data is not eligible for cycling segment leaderboards. Virtual Rides are not eligible for Strava Challenges at this time.
Indoor recording tip:
If you cycle indoors with sensors for speed, cadence or power, it is best to disable the GPS on your device while recording a stationary activity. This will help with correct analysis of your data such as distance and speed.
If you didn't record your indoor session with a device, you can still enter the data manually on Strava.
You'll get the credit for the training and all you have to do is enter the basic fields like duration, time of day, date, and distance. To create a manual activity go to "Upload Activity" on your account and choose "Upload an activity manually".