Running in the Sunshine

The Can Lake 50 Ultras were held the same weekend as the Chicago Marathon and had similar weather... low 52, high 80 degrees and not a cloud in sight.  Last year race day dawned with a low of 35 warmed up to only 61 degrees with similarly clear skies.  With similar numbers of runners both years, it was a good test of the effects on heat on running performance.  The following table compares data from the two years.

Most of the effects are what you would expect.  The heat slowed down the runners; the median or middle of the pack in each race was 25-27 minutes slower than last year and the number of runners who finished outside the 12 hour time limit was up.  Running many hours in the heat more than doubled the number of runners who dropped out.  Leg cramps were a common problem reported by the DNFs and many finishers.

Note that folks making the Can Lake 50 their first ultra marathon finished at a higher rate than the whole field over both years.  The Can Lake race team works very hard to support first timers so their first race is a successful one.

We probably should have expected the big bump up in the number of no shows (runners who entered the race and then did not show up on race day).  Hot weather on race day was forecast for several days before the race, long enough to give one second thoughts about spending all day running around the lake.