By default, athletes are able to update their registration details, including any custom field responses as well as their division, until a score is recorded for their account. You can restrict this registration access for any of your competitions using the Registration Access toggle.
To restrict access:
Select "Advanced" from the competition's dashboard.
Click on "Registration Access".
Disable athletes' ability to change their registration by unchecking the "Allow athletes to update their registration" box, then click "Save".
Unchecking this option will prevent athletes from being able to update or change their registration information. One example of when it might be useful to disable registration access is when you have passed the t-shirt deadline and no longer want users to be able to update information such as their t-shirt size or team name, so that you can lock down and submit your shirt order.