Emily Oster surveyed a collection of studies on walking and running speeds, which she summarizes at FiveThirtyEight.
Oster concludes:
If we take this research at face value, we learn a few things.
First, some exercise reduces your risk of death.
Second, the optimal walking/jogging exercise is light to moderate jogging.
Whats the Optimal Speed for Exercise?| FiveThirtyEight
Photo byGiorgio Galeotti.