@roger,
I read a million running articles back in the day. Maybe something has changed re muscle needing a bit of time for repair. I can figure that would be possible. I can see running 20 miles a day five days a week for a few, but I don't think it is good for you. I might have articles to back me up on my computer but I'm not in the mood for linking. But, I can imagine it, the intensive running. (but, wait, why?) I've seen people walk up mountains with large weights on their shoulders. But that is need.
Re the Tarahumara, I thought they were from Venezuela, but that was when I first knew about them. Not so much, I see. The guy who later became a boss but not yet, somewhere in the early seventies researched their muscle physiology, Jim Peter and Robert Barnard, if I remember. Jim Peter eventually started CIL (Clinical Immunology Lab) and that became Specialty Labs.
Here's a business type obit on Jim Peter, originally a muscle physiologist -
http://www.darkdaily.com/james-peter-m-d-ph-d-founder-of-specialty-laboratories-dies-of-cancer
He and I butted heads a couple of times, about other people, but he was very sharp. He gave me a good kick off for my landarch boards, not that they would know who he was.