There might be a way...keep in mind I'm new to CB also but I've kind of been looking for similar thing.
This is what I would suggest you do...
First create a new "tab" - Run History, for example - that will be added to the profile page (which each user can edit for themselves)
Then create new fields in the Field Manager that you can later assign to the Run History tab. If you want them to be able to keep the history for 10 different runs create the fields for example: 1K time, 1k date, 2K time, 2K date etc.
Also, if you wanted to create a "report" that shows what everybody's info is for just the 10K run then you can create a "list".
Go to Youtube and search Community Builder and look for the lesson series by a guy called QuicSite. He also has a website at
www.planettucker.com
where you can access the tutorials.