Suunto App and Sports Tracker are collaborating to bring you Suunto app. Both apps are connected and share the same community. If you are previously or currently a Sports Tracker user and use the same login credentials for Suunto app as for Sports Tracker, the account is connected to both applications. In this case your workout history will be synced with both applications.
If you want to start fresh with Suunto app, create a new account with a different email.