I think efficiency and impact are generally inversely proportional, so you're good either way. If walking isn't near your aerobic limit then you'd be much bett

I think efficiency and impact are generally inversely proportional, so you're good either way. If walking isn't near your aerobic limit then you'd be much better off doing something else for exercise than making your stride less efficient. Walking as a kind of meditation or just to relax might be quite valuable. Then, the more efficient (relaxed) the better.