A.M. Did 6x400 spread throughout the run. I timed it so that I would be doing two of them in the last 1.5 miles. Again, the idea was to test the glycogen level as well as to train the nervous system to override the low fuel negative feedback. I believe a quarter is long enough for that particular purpose. The reasoning is this:
a) In a low fuel situation I cannot run a fast quarter, and pain/slowdown is felt particularly in the second half of it
b) In the past I have been able to correct the symptoms of low fuel shutdown by doing a few fast quarters a couple of times a week.
c) There was a study a few years ago that demonstrated that a 3 minute bout of maximum effort greatly enhances the ability of the body to absorb glycogen over the next 24-28 hours. I do not remember all of the science behind it, but I believe the basic idea is that if you squeeze the toothpaste tube very hard for a brief moment the vacuum creates a momentum for the new toothpaste to come in if a source is available.
From this I intuitively conclude that a couple of quick quarters at the end of any run will stimulate glycogen absorption and teach the nervous system to work with less fear in a low fuel situation. A good marathoner must learn how not to panic when low fuel signals are being received, and it must happen on both the conscious and subconscious levels. After having run 50+ marathons I am OK on the conscious level, but the subconscious is much harder to train.
So anyway, the theory aside, I did this; 74.5 up - 71.1 down - 74.4 up - 70.8 down - 72.3 rolling and 69.7 down. Total run was 12.2 mile. Benjamin did 3.2, Jenny and Julia 2, Joseph 1, and Jacob 0.5. Joseph asked me during the family scripture study what "endure to the end" meant. I explained the idea using examples from running. He has been remembering it during his runs.