You may use the Fittest Fire App to store your workout data locally without ever creating an account. In this case, no personal information is collected at all. All your workout data is stored on your personal device.
If you create an account to get points for exercises, your email address and any exercise data you send to the server will be stored in a database. The purpose of storing your email address is so you can login and reset forgotten passwords. The purpose of storing exercise data is to calculate points and also to serve as a back up.
All membership payments are handled through Apple and Google respectively. Fittest Fire does not store any credit card information.
Fittest Fire does not share any workout data with third parties.
All network operations through the Fittest Fire App are secured using HTTPS.