Monitoring fitness using a mobile device

A method comprising:

• initiating, by a first computing device associated with a first user, a first activity challenge and including one or more other users;
• receiving, during the first activity challenge and from a second computing device associated with a second user of the one or more other users, a request to adjust the first performance level associated with the first activity challenge to a second performance level;
• initiating, during the first activity challenge, a second activity challenge associated with the second performance level and including at least the first user and the second user;
• and
• outputting, in response to initiating the second activity challenge, a user interface displaying first information related to the first activity challenge with second information related to the second activity challenge.

A method comprising

• collecting, by a first computing device associated with a first user and while the first user is participating in a first activity challenge associated with a first performance level, athletic activity data of the first user;
• receiving, during the first activity challenge and from a second computing device associated with a second user participating in the first activity challenge, a request to participate in the first activity challenge with the first performance level adjusted to a second performance level;
• sending, to the second computing device, an indication that the request to participate in the first activity challenge with the first performance level adjusted to the second performance level is accepted;
• and
• outputting, in response to receiving an indication that the first activity challenge has been adjusted to be associated with the second performance level, a user interface in which first information related to the first performance level is updated with second information related to the second performance level.