As human beings are called as a bipedal animal, we must make use of our legs to walk and move here and there which is not at all happening because of vehicle usage and advent of transport media.
Walking a good distance say 3-5 km on a daily basis is must if you really want to get a strong spine, strong legs and good cardiac compliance and resilient body.
In defence, the word'parade' is used and practiced so much so that every defence personnel develops the habit of walking and thus maintain their fitness.
The first thing that the child learns is crawling and then later on standing and walking a good distance and the toddler just run in-house as this is one of the most natural ways of our existence. Remember walking is the first milestone before talking that's how probably walk the talk is more relevant as per the milestone development theory, isn't it!
Daily walking increase levels of endorphins, activates glucagon and reduces insulin thus achieves the best balance and rejuvenation.