Given the hot weather lately, I thought I would do some analysis on the impact of the weather on the results for our favourite trail run.
Temperature data: I got the hourly temperature data for the Mt Boyce AWS on the days of the race. I took the average of the 8am to 2pm readings to get the “average” local temperature over the time that most people are out on the course. No data was available before the 1990 race, nor for the 1997 race.
Race time data: I took the median and the 25% and 75% quartile times of the number of people who started. That is, if 800 started, I took the 200th, 400th and 600th time.
Years covered: I looked at three sets.
1990-2008 covered all the data I had available (although I removed 1991 because it was a big outlier.)
1996-2008 was interesting because I suspect that some of the earlier years are not representative of the range of people who enter the race today.
2001-2008 was done because that is when the last change in course and time limit happened, although the temperature range since then has been pretty narrow so you don't get a lot out of it.
For each of those data ranges the average 25% quartile, median and 75% quartile race times were:
1990-2008 5:06:02, 5:41:58, 6:20:38
1996-2008 5:10:05, 5:45:47, 6:23:03
2001-2008 5:06:53, 5:42:25, 6:19:44
and the sensitivity to a one degree change in temperature is
1990-2008 0:02:14, 0:02:14, 0:02:28
1996-2008 0:02:28, 0:02:49, 0:03:37
2001-2008 0:02:04, 0:02:44, 0:03:42
In case you a wondering what all this means, if you are, say, about a 5:10:00 6FT runner, then (based on the 1996-2008 data set) you should expect your time to increase by about 0:02:28 for every additional 1 degree in temperature - so a day 2 degrees hotter than average should yield a 5:15:00 time. If you are a 6:20:00 runner, then on a 2 degree hotter day you should run about 6:27:00.
It also means that the difference between the hottest and the coldest days of the race (about 10 degrees difference) should yield times around 27mins different for the median runner.
For every 1 degree change in temperature, runners should expect to add 2-4mins to their final time. So a 5 degree hotter day should add 10-20 mins. Just out of interest, last year was about 3 degrees cooler than the average, which gave most people a headstart of around 6-12 mins.
None of this analysis takes into account other factors such as humidity, rain, wind, effects of a muddy track, depth of Cox's river, trees down in Nellies Glen, changes in cut-off times, changes in the route, changes in the distribution in people running the event etc. However, looking at the attached diagrams, the temperature seems to be a pretty good indicator of the median time. With an R^2 of around 80%, Occam wouldn't be recommending anything more complicated.
If anyone wants to do their own analysis, I am more than happy to fwd the source data on.
Good luck with training over last few weeks,
Edited by hatless, 11 February 2009 - 02:44 PM.