This Runner’s World article from 2007 shows that 5k runners may just hit PR’s if they take their first mile 3% to 6% faster than they usually do.
But then why do world class runners keep even and/or negative splits when they race? According to the article, elite runners keep their pace up right from the start and know how to run right on the edge of their anaerobic threshold, which of course is much higher than most runners.
I’m torn on this one because I really like to see runners take their races out conservatively. But maybe they shouldn’t. Perhaps it is best, in races at 5k or less to take out the first mile reasonably fast and then hold on for dear life.
When races are 5 or more miles, however, I wonder about diminishing returns on the fast start approach. The 5k is a relatively short race and an exhaustive start won’t catch up with a runner in quite the same way as if they have a few more miles to go.
Regardless, the most important part of increasing your chances of having a successful race is to come up with solid a race plan. And the best possible scenario involves a couple alternate plans to account for conditions that may be a little different than anticipated.