Running the Tangents - Short Course Prevention Factor USATF
As I watched the elites race the Bolder Boulder, I was amazed at how some of the runners, in particular Dmessew Tsega, failed to run the tangents. A tangent is a line that just touches a curve, it doesn’t touch the curve nor does it intersect the curve.
The tangents are also how the race course is measured. Often times it’s not possible to run the tangents, due to the crowd, etc. thus if you are unable to run the tangents you will run further than the advertised race distance. To run the tangents, you must be mindful at all times, looking ahead, and knowing how you will handle each turn of the race.
I imagine Race Directors get an earful from every runner who owns a Garmin who complains that the race is too long. From my personal experience, my Garmin was always long and these were USATF certified courses, but the margin of error was generally <1%. I trust that the USATF courses are marked correctly, however, I'm sure that there are mistakes made and some USATF courses are not correct. However, the only time I am skeptical is if my Garmin has the course longer than 1% or if my Garmin has the course short. But, a large part of that error is the runners inability to run the tangents.
USATF course certification rules state that
Because it is difficult to follow the shortest possible route perfectly, an extra length factor of 0.1%, called the short course prevention factor, is incorporated into the calibration procedure. Use of the factor ensures that your course will not be short, even if you make small errors in following the shortest possible route.
That means that in a marathon, the course is measured 42.195 meters long.
That is, if the marathon is not Colfax.
A couple of years ago a large technology manufacturer held an experiment in the London Marathon.
Several age group/sub elite runners had GPS watches or whatever and were instructed as follows
First runner - run on the marked line on the road come what may - (The offical 26.2 miles). (He had a helper to fetch him drinks etc)
He ran 26.2 miles to within less than 1%
Second runner - to please himself - if he felt like running on one side of the road to run with a pretty girl or sightsee or whatever - he could do it. He ran around 27 miles
Third runner - To go with the flow and get taken by the flow of the crowd or runners around him. To not concentrate on the way forward at all..
He ran almost 28 miles…
That’s an interesting idea. I had never though to check the margin of error on my GPS. Nor had I thought to try and find the “official” course. I need to work on not running around people and zig zagging as much.