Wednesday, October 20, 2010

Do your femurs make you look lazy?

Reposted from One Day at a Time.

I've been reading interesting things about femurs lately!

For instance, if you take a cross-section of a femur at around the middle of the shaft, the shape of that cross-section can indicate the individual's activity level.

Bones, like muscles, grow and develop in response to physical exercise over time. Ambulatory activities like walking and running excercise the leg muscles and expose the bone to mechanical stresses in the anterior-posterior (front to back) direction. The result is that a person who does a lot of long-distance walking or running during his or her lifetime will have a femoral cross-section that looks vaguely elliptical, with the bone being thicker on the anterior-posterior (front ot back) axis than in the medial-lateral (side to side) direction. In other words, if you walk or run a lot, your femur will be thicker than it is wide.

More sedentary types, like most modern Americans, will have femoral cross-sections that are pretty much symmetrical in all directions, since the bone hasn't been exposed to much greater stress on any particular axis.

My fiance, when I told him this, was instantly self-conscious about the possibility of having round midshaft femoral cross-sections. He makes me laugh. :)

Anyway, that spiffy bit of triva came from Skeletons in Our Closet: Revealing Our Past Through Bioarchaeology by Clark Spencer Larsen.

It was one of that set I rescued from the flea market a couple of months ago, and it may well be the best fifteen cents or so that I ever spent. Larsen's writing style is engaging and easy to follow, and he works his wonderfully clear explanations of osteopathology and analysis methods into the unfolding story of his own research in the Great Basin, which is in turn set against the larger story of the global transition from hunting-and-gathering to farming and its consequences for human health and lifestyles.

I'm actually taking notes as I read this one, because it's interesting information and very well presented, and because I'm making a concerted effort to maintain both decent study habits and passable currency in the field between now and the time I start back to grad school (hopefully January of 2012). So far it feels like it's working.