Via the New York Times, information about the mental benefits of exercise: "Learning in midlife to juggle, swim, ride a bicycle or, in my case, snowboard could change and strengthen the brain in ways that practicing other familiar pursuits such as crossword puzzles or marathon training will not, according to an accumulating body of research about the unique impacts of motor learning on the brain."
Key points:
"...running and other types of physical activities increase the number of new brain cells created in parts of the brain that are integral to memory and thinking."
"...learning a new physical skill in adulthood, such as juggling, leads to increases in the volume of gray matter in parts of the brain related to movement control."
"...increased myelination of neurons in the animals’ motor cortexes. Myelination is the process by which parts of a brain cell are insulated, so that the messages between neurons can proceed more quickly and smoothly."
In short, the physical activity of exercise stimulates the growth of new brain cells, and learning new movements makes it easier for neurons to carry their signals around.
Nordic walking can yield those 2 benefits. The benefits from the physical activity are self-explanatory. Learning to Nordic walk also requires learning some new motor skills, something that requires you to focus on what you're doing. Learning new motor skills promotes that myelination mentioned in the article.
Notice in this very short video mention of learning new motor skills:
