When you're training for a marathon, shorter tune-up races offer a few benefits. First of all, they're great workouts, because you can always push yourself harder in a competitive environment than you can in a regular workout. Also, they reward the hard work you do in training with a chance to post a time you're proud of, win a ribbon, or whatever. To me it would be a shame to train for four or five months just for one race--my marathon.
Another benefit of tune-up races is that they provide information that you can use to determine whether your fitness development is on track with respect to your marathon time goal. If you expect to run X time in a marathon Y weeks from now, then you ought to be able to achieve Z time in a 5K, 10K, or half-marathon today. Of course, there's no formula that you can use to calculate these variables with scientific precision, but the combination of a race time equivalence table or calculator and some common sense will give you good hunches.
I like to use the race time equivalence table in Jack Daniels' Running Formula and the race time equivalence calculator on Greg McMillan's website (www.mcmillanrunning.com). Here's how the whole thing works. My goal time for the marathon I plan to run in December is sub-2:40. According to Jack Daniels, the 10K equivalent of a 2:39:55 marathon is 34:30. According to McMillan, it's 34:05. What these calculations mean is that, if I were to run a 10K race instead of my marathon on the day of my scheduled marathon, after having completed all of my hard training and a good taper, I should expect to run somewhere in the low 34's, if indeed my marathon goal was appropriate.
Now then, how fast should I expect to run a 10K tune-up race taking place 11 weeks before my marathon
when I should be well on my way towards peak fitness, but still with a ways to goas I did last weekend? Combining the above calculations with common sense, I set a goal to run 34:55.
Well, I ran 35:34. But I'm not ready to hit the panic button just yet, because the racecourse that was promoted as pancake flat turned out to be anything but, and two miles of the race were run into a vicious headwind. However, I don't like saying "shoulda, coulda, woulda," so I decided that this particular tune-up race didn't tell me much about whether I am on track to meet my marathon time goal.
So I'm looking ahead to my next race, a half-marathon on October 14. If I don't run 1:14:50 or better there, I will hit the panic button!