Last Saturday I did the adidas Irish Runner 5 mile race in the Phoenix Park. My first mile split time was a unbelievably fast 5:07. As this was 8 seconds faster than I have ever run a mile I figured that the mile marker was in the wrong place.

The rest of the mile markers seemed to be placed reasonably accurately (well, mile 3 seemed a little long) but I finished the race a full minute faster than last year (29:47 vs 30:50). I was suspicious – I felt that something must be wrong.

Back home I was reading the boards.ie thread on the race and someone questioned whether the course was short. A number of others soon followed with the same conclusion, with Garmin and similar data to back it up.  My Polar HRM measured low too (it normally measures low but this time it was extra low).

One guy developed a chart for people to use their chip time to extrapolate their time for a full 5 miles.  The chart only listed whole minutes so I wrote a PHP script to extrapolate any time.

I posted this on the thread and it was well received. I then posted it to the Dublin Marathon page on Facebook and I saw a jump in visits to the page during the day.