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Sunday, April 19, 2015


"The pavement was his enemy!" A line from the 1989 delightful film Twins starring Schwarzenegger and DeVito. Schwarzenegger, as Julius Benedict, delivers the line when a robber on a motorcycle tries to relieve him of his suitcase but cannot overcome Benedict's vice-like grip and comes crashind down on the sidewalk. The robber's buddy asks Benedict what he did and he says, "I did nothing! The pavement was his enemy!"

I bring the memorable line up because in November of 2012 I broke my foot. The medical term is a metatarsal stress fracture, specifically of the second digit. That's one toe over from the big one. The metatarsal bones are the long bones of the foot, the ones between the toes (phalanges) and the midfoot, those bones that form the arches of the feet and have fancy names like cuboid and navicular. Here, a picture is worth a thousand words:

Metatarsal stress fractures are a common injury related to running. Soldiers often get them, after marching great distances in uncomfortable shoes. What often happens is a runner increases mileage too quickly and the bones are unable to adapt to the added stress. Since I had increased my weekly miles from about 30 miles in June to as many as 80 miles around the time my foot cracked, I thought overzealous training was to blame. And I was running most of the miles barefoot, and the injury occurred in the fall, when sunlight is not as plentiful, and as I rely on the sun for vitamin D, and lower levels of the vitamin are associated with weaker bones, there were other factors to blame.

But one thing I had never thought to consider was terrain. I run from my house, and the first couple miles are all on asphalt. Then I enter the city, where traffic leads me onto the sidewalk (pavement). For those who haven't thought about it (and I hadn't until recently), there is a big difference between the black material that lines roads (asphalt) and the white, smooth stuff you see on sidewalks and bike paths.

Asphalt (streets) deflects forces downward while concrete deflects them sideways. In other words, streets employ the dirt beneath as shock absorbers, while concrete does not give. The result? Concrete is 10 times harder, by one engineering measure, than asphalt! Ten times! Does this mean that running 80 miles mostly on sidewalks is like running 800 miles on streets? The math would say yes.

As I increased the miles I found myself running more alongside traffic, so a disproportionate amount of mileage was occurring on the much harder surface of concrete. Now I can explain the joint aches and pains. And possibly the stress fracture. Few are fortunate enough to live in or around parks, mountainsides and trails. If you do, log as many miles as you can on runner friendly surfaces like grass and earth - unless of course you are training for a road race, in which case you'll need to accustom your legs and feet to pounding the pavement. But if like me you must needs run most or all of your miles on the road, opt for the street as often as possible over the sidewalk. This may involve running side streets rather than more heavily trafficked major thoroughfares, which is a good idea for other reasons, like avoiding smog.

(An easy way to tell the difference betwixt pavement and asphalt is pavement is generally white/off-white and cracks while asphalt is black or gray and crumbles; not all streets are asphalt so look before you stride.)

And if you run in the street, run as often as you can in the middle of the road, avoiding traffic of course. This will spare you the gutters and the leg length discrepancies they simulate. This happened to me in medical school, when running 6 miles along the shoulder of a Louisiana highway each day before my hospital shift gave me a nasty dish of plantar fasciitis and a side of hip bursitis.

Ah so many conditions! So many rules! Can't anybody just run already???

Excuse the outburst. Be friendly to your feet. They're the only ones you'll ever have. Your kindness will be repaid in spades.

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