I was struck by a recent article on Slate.com about carrying objects on your head, aka head porterage. The article, Head Case - The art and science of carrying things on your head, by Jessica Dweck, outlines briefly some of the pros and cons of head loading.
Amusingly, the article says:
Based on studies [. . .] researchers have found that people can carry loads of up to 20 percent of their own body weight without expending any extra energy beyond what they'd use by walking around unencumbered. Above that figure, however, metabolic costs seem to increase proportionally with load weight. [. . .] The subjects in these studies began head-loading as children and had developed a peculiar gait that's one-third more efficient than the one we're likely to use.
Interesting, eh? But "For untrained controls who have not had years to strengthen the right muscles and build up spinal bone density, carrying things on your head actually requires more energy than using a backpack." So add in increased spinal bone density and better strength in the appropriate muscles (presumably the neck and spinal erectors, plus probably the abs since they'll help keep you in a proper spinal alignment as you move) to that more efficient gait.
The article reminded me of a book I read (and didn't review, since it was before I had this blog) called Ageless Spine, Lasting Health: The Open Secret to Pain-Free Living and Comfortable Aging by Esther Gorkhale. Her book makes a case that our way of living negatively affects our posture. What's more, it also punches a few holes in the idea of the usual "stand up straight" advice we get. She's centered entirely on lining up the spine and hips and head in a natural way to reduce the stress on your body from poor posture.
Naturally, her book contains a number of pictures of men and women carrying head loads.
I think I'll have to add that book back to my "to read and review" list. The ideas are interesting, and it's worth investigating. Not that I see myself adding head loading into my workouts straight away, but anything that equals improved "spinal bone density" sounds like it's worth reading. In the meantime, enjoy the article.