A method is provided, including: processing requests from a plurality of users to join a group event, the group event defined for an activity metric for each of the plurality of users for a period of time； analyzing the activity metrics of the plurality of users to determine a ranking of the plurality of users based on their activity metrics, and to identify a change in relationship between activity metrics of two or more of the plurality of users； generating a message, wherein generating the message includes, identifying, based on the identified change in relationship, one or more user accounts of select ones of the plurality of users to receive the message, selecting a message template based on the identified change in relationship, and populating the message template to generate a message describing the change in relationship； sending the message to the one or more user accounts.
