With more activity tracking sites being able to export to and import from each other you run the risk that your activity is uploaded multiple times following different menu selections.
Duplication on MyFitnessPal by following these uploading menu selections:
Duplication on Strava by following these uploading menu selections:
Most sites try to detect double activities to prevent this issue but this may sometimes fail, so it is best to not rely on this.
Check the import/export settings for the activity sites that you use and disable any duplicate paths.