I've been struggling with setting a goal for my Fall Marathon. I already have one Marathon under my belt for 2010 but with 16 weeks between the summer and the fall one, what goal do you go for? I needed to take down time between the two (three weeks) but now that my mileage is coming back up, I need to set a time goal (running two marathons just for fun gets old).
The logical side of me wants to just set the goal and work towards it – put in the speed, tempo, and long runs based on a stretch goal – like take a half hour off my last marathon (lose one minute per mile by pacing). But the emotional side of me knows that type of commitment could make running a chore.
When I'm faced with this decision, I use the 2.1 half measure rule. Use a race that is half the distance of the goal race to determine a 'reachable' goal. For instance, if you wanted to run a 10K in 50 minutes, then you need to run a 5K in 23:48 (50 minutes x 60 seconds = 3000 seconds/2.1 = 1429 seconds/60 seconds = 23 minutes, 49 seconds).
I think the best way to do this is not to set a goal for the longer race by targeting the shorter race's time. In other words, do it the other way. For the 5K, you need to run the race first, push yourself so you leave it on the course (know you couldn't have done it any faster) and multiple by 2.1. That's what I plan to do in two weeks at a Half Marathon I have on the schedule.
Why half the distance? Because it's the only reliable measure. Based on my 5K times, I should be easily beating a 2 hour Half Marathon time. But running 3.1 miles isn't a great indicator for a 13.1 mile race. I have found that even after having a great 5K, 10K, or even 10 mile race time – that it doesn't equate to the predicted Marathon time.
I do believe in the predictor charts that give you 'expected' race times based on various distances. The trouble with them is that runners use them like a bible. I believe the charts are more of a predictor of your VO Max race times, then your actual race times. They tell you that you have the lung capacity, stride and ability to run a race at a predicted time. But you still have to develop the endurance for that distance.
So even after I race the Half, I still will have to put in the 20 mile long runs to get the endurance to be able to actually 'race' the Marathon distance even if I know the predictor charts say I should be able to do it at a predicted pace.
Try this the next time you move up the mileage on your races and let me know if you don't find the same result.