I walk around my office complex almost every day at lunch. I began it as a way to help heal from the repetitive stress injuries that come from working on a computer all day. Quickly I noticed an increase in aerobic capacity and hiking endurance. I believe that it’s because my walks add to the work I already do at the gym, not just because I walk at lunch. The more you exercise (within limits) the quicker you notice improvements. I’ve also noticed that it’s a wonderful way to decrease stress. My body relaxes at the 30 minute mark, and the last ten to fifteen minutes I feel like the stress of the day has evaporated. It’s very refreshing.
I also use this time to let my mind wander or pay attention the trees and wildlife that surround my nature park - maple, willow, live oak, roses, lavender, jasmine, crows, other birds I cannot identify, ants, bees, bumble bees, crickets, etc. Recently, I created a simple prayer bead bracelet that I use to recite a chant for my 13 virtues. I can chant them silently to myself, or ponder what I mean by wisdom, or what integrity really is.
More than walking, I think what is truly valuable is giving my mind 45 minutes most days to do some semi-constructive thinking or just time to let my mind and body relax. Seated meditation can do this, but walking enables me to practice all sorts of observations as well as meditation techniques like breath control or chanting in a totally different context than the seated meditation style.