With an exercise app, mine compares me to the average for people using the app but am curious about something.
Wouldn't those who actually use the app be those who tend to exercise more so you are not really comparing yourself to the average person but instead others who value exercise?
I suspect so, but it would also include people, like my parents, who are using phone apps to track their daily activity (having regard to their age), also people (like I was) who are supposed to be limiting their activity while recovering from injury or undergoing rehabilitation. It would, likely, only include persons who are engaging in the same type of activity (i.e the app you are using may not be an app that is commonly used by swimmers).
And those who are just curious about exercise. Depending of course on the detail of information recorded and compared in the application.