Friday, February 11, 2011
Change of Season
I took a 3 year hiatus from true winter running while I lived in Texas. Laredo rarely got below 40 degrees and we never saw snow while I was there. Despite the time away from it, when I returned to the north, I found that I hadn't lost a step in regards to winter running.
The ability to wear shorts year round I long ago wrote off as being a simple case of mind over matter. I didn't mind the cold, therefore it didn't matter. My ability to keep my feet under me no matter how slick and icy the roads became, I never really thought about. It wasn't until a few years ago that I even bothered to take notice of my luck.
About midway through that winter after hearing many a runner complain about their many slips and falls something clicked in me and I finally started to wonder why I had never joined their ranks. Sure I've slipped many a time and done all sorts of spins, twists and maneuvers that would make even the most experienced ballerina jealous, but I had never gone down. That isn't to say I never fell, but those few times I had was not because of slips, but rather from tripping over an unseen object hidden beneath the snow on the trail upon which I ran. Tripped and fallen yes, but never slipped and fallen on the ice.
It took me a while to figure out a possible reason, which it wasn't until this winter that I finally felt was confirmed.
My normal stride is fairly long and as a result my heel would strike well in front of my body at a sharp angle to the ground. This was fine most of the year, but on ice it would prove dangerous. Only a small part of the sole would come into contact with the ice, which would lessen traction, and the angle would velocity across the surface of the ice. By shortening my stride I was allowing the heel to strike at closer to a 90 degree angle which would bring more tread into contact, therefore more traction, and would provide less angular velocity across the ice.
I won't try to go into physics to explain this, but it's a relatively simple idea. A simple way to look at it would be to think about an object sitting on ice. If you give it a push from the side it goes sliding across the ice. If you push straight down on it, it doesn't move. From there it is easy to see that as you vary the angle between straight down and directly from the side that the distance the object will slide varies. Same thing for our feet. That's why when most of us walk on ice we do so gingerly, carefully putting our feet down directly below us, flat footed.
Despite not realizing it, I had for many years been changing my stride every winter to maximize traction and returning to my optimal stride as winter passed. I would still slow further and run cautiously on ice, but my slipping was minimal.
As I was running on a very slick, icy road, I realized I was running normal speed for dry ground and I hadn't shortened my stride. After thinking about this for a while I realized that when running forefoot my foot was landing directly below me at a 90 degree angle to the ground. This meant no angular velocity. In addition I was maximizing the amount of tread in contact with the ground, further improving traction. At least to me this confirms my theory about the shorter strides.
I still don't know why or how my body just automatically made this change in stride, but I'm sure I've been doing it since day one. I remember my freshman year my track coach getting on me all through February and March about lengthening my stride. He was same coach I had all fall for cross country and he never had problem with my stride the entire season. Every spring and fall while I was in high school he never commented on my stride, yet every winter same thing, lengthen my stride.