The e-mail address you use to log in, your name, and the workouts assigned to your account are stored in the database.
Additionally, there is some preferences information attributed to your account, such as the exercise equipment you selected the last time you created a workout, and a log of site transactions, such as when you last logged in.
Check out the Manage Account page to see what this site has stored about you.
If you wish to purge record of yourself from this site, Contact Matt.