I walk while typing. It's not difficult. What I DON'T walk while doing is - really cognitively challenging tasks OR learning something difficult/new, because

I walk while typing. It's not difficult. What I DON'T walk while doing is - really cognitively challenging tasks OR learning something difficult/new, because that is markedly more difficult while walking. If I really need to focus because a task is well outside of my comfort zone then I will almost always be sitting. Luckily, software development isn't always that kind of work (though it often is!)