On the Internet, there is a lot of discussion by people about how they run "naturally". Some will say that they naturally run by landing on their heels first and rolling through to their forefoot.
I would ask them if they are doing their allegedly "natural" style of running - shod or unshod. ? We are not born with shoes on our feet - so if anybody is unsure of how they "should" run - just go to a nice grassed sports field ( one where they are no hyperdermics laying around ) and do some running with no shoes - slow. medium and fast. I am sure that you will very quickly find that you do not -- CAN NOT land on your heels. It is not possible without destroying your heels - as heels are not designed to take that impact. So - if you do currently run "naturally" on your heels, I would say that it is more of a developed habit created by wearing shoes with thick padding in them.
Try it - you will see what I mean .
There are plenty of vids available regarding good running form here youtube.com/results?search_...
And look at this poetry in motion
-- if only I could run like him!!!!!