Oh, for me it does. I feel an enormous mood lift from a bit of exercise, especially if it takes place outside on a sunny day, and it kicks in pretty quickly. I agree walking may be not quite intense enough to get much of an effect (though I think it does a bit, for me), but I cycle to and from work (not fast or anything; it's a short distance, though a tiny bit hilly, and I'm a very casual cyclist) and that does give me a little boost most days, and some mental space between work and whatever's next. Of course, it sucks in horrible weather.
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.