The FAQ currently contains the clause:
practical, answerable questions based on actual problems that you face
which people are using on this site to mark theoretical questions as off-topic. For example see this question: Body's adaptations to training in hot conditions?
I looked at the FAQ from various other stackexchange sites, including mathematics, physics and biology, all of which contain the same clause. However in mathematics, physics and biology, theoretical questions are frequently encountered without having to explicitly state how the theoretical question related to the asker personally. For example see these questions: https://biology.stackexchange.com/questions/6794/do-adjacent-axons-in-a-nerve-influence-each-other, https://physics.stackexchange.com/questions/47368/limitations-on-how-far-one-can-travel-in-the-universe.
So why then is the FAQ worded the way it is? My understanding is it is because of what comes immediately after in the FAQ, that is,
Chatty, open-ended questions diminish the usefulness of our site and push other questions off the front page.
I therefore believe that "practical, answerable questions" can include theoretical questions like the ones posted in the physics, biology and mathematics stack exchanges, and also like the question from fitness stack exchange which I linked above.