The New York Times, on The Benefits of a Lunch Hour Walk:
A new study finds that even gentle lunchtime strolls can perceptibly — and immediately — buoy people’s moods and ability to handle stress at work.
[...]
On the afternoons after a lunchtime stroll, walkers said they felt considerably more enthusiastic, less tense, and generally more relaxed and able to cope than on afternoons when they hadn’t walked and even compared with their own moods from a morning before a walk.
I've been a long-term fan of the lunchtime walk. Sometimes it's as simple as walking 10 minutes to get a sandwich, and when time permits it's 30-45 minutes with a brief lunch stop along the way.
My mid-afternoon productivity is severely lacking if I don't get even a short walk at lunchtime - and my back pain during the week becomes unbearable if I miss a few walks.
A short lunchtime walk is a critical part of my being able to contribute to society.