A.M. Decided to run a little less today. Here is the theory behind it. There are three important factors to be aware of when trying determine the optimum length of the run. Aerobic stimulus, fatigue hormones, and strength hormones. Aerobic stimulus increases in proportion to the length of the run. The fatigue hormones increase in proportion to the length of the run as well. If the fatigue hormones overpower the strength hormones, you may get stronger cardiovascularly, but it does you no good because the muscles are too weak to use the aerobic power. The tricky question is at what point the fatigue hormones begin to overpower the strength hormones. I am suspecting this critical point varies not only from individual to individual (obviously), but also within the same individual based on his level of strength at any given time. So if the strength hormones are doing well, you can throw a few more miles at the body, and you will do fine. If not, they get overpowered.
I did notice over the last month that running only 8-10 miles in one run compared to the normal 12.5 correlated with the increase in strength, and then returning to 12.5 gave me a decrease again.This was rather odd, I thought, because in the past I did not notice any such difference. In fact, in 2007 I ran 13 miles in one run followed by another run in the evening with no loss of strength. So I thought if anything, I would only get a reduction in the aerobic power from running only 10 instead of 12.5. But solutions are often found by exploring odd possibilities. A good rule of thumb is that a solution to a difficult problem often involves an odd move. If it did not, you would have seen it already, and the problem would not be difficult.
So I decided to see if that was a coincidence, and ran a bit less today - 10.25 including kids runs. Benjamin did 4, Jenny, Julia, and Joseph 1.5. I did a couple of pickups on the trail just for fun.