When I read this comment, it strongly reinforced the part of my mind that was wondering how many hobbies existed that couldn't be construed as rationalist exercises if one wished to do so. However, you may want to discount me slightly because I'm not a fan of sports at all, and am sometimes slightly irritated at seeing sports on TV for reasons that I have not paid much close attention to.

With that said, I propose that we come up with a list of hobbies that shouldn't be considered "rationalist," and see if anyone else can come with a convincing enough note regarding them to convince us otherwise.

So, to semi-stick my head out, my hypothesis is that the space of hobbies that could be considered "rationalist" is too large to be very useful to us. Grouping these according to the skills that they purportedly train may help counteract this; perhaps it would be useful to rank skills in each group so that we could quantify opinion on which ones increase certain skills more than others.