This is a privacy nightmare. Even with anonymized userids the data was far too user-specific.
The details were released by Strava in a data visualisation map that shows all the activity tracked by users of its app, which allows people to record their exercise and share it with others. The map, released in November 2017, shows every single activity ever uploaded to Strava – more than 3 trillion individual GPS data points, according to the company. The app can be used on various devices including smartphones and fitness trackers like Fitbit to see popular running routes in major cities, or spot individuals in more remote areas who have unusual exercise patterns.