Thanks, R_Tellis. I think what frustrates me the most is not that I can't create an activity called "Crossfit", but that when I settle for one of the options offered ("Train"), it still reverts to "Running" when synced. Perhaps I can try creating my Crossfit-specific profile from from a category I don't typically use, such as "Cardio". I initially considered "Strength", but didn't want the rep counting.
There's an app in the IQ store called "Any Activity" that would solve this issue.