You can add an activity to the Strava website even if you didn't record it with a GPS device.
Simply enter time and distance for an activity (like a ride, run, hike, walk, etc). This is a great way to keep track of your training even if you aren't able to record with a GPS device.
To enter an activity manually:
- Log into Strava
- Click on "Upload" at the top right corner of the page
- Select "Manual" from the drop down menu
- Select your Sport, enter the other required fields, and click "Create"