Reading Marathon Training: A Scientific Approach by Enrico Arcelli and Renato Canova for the forth time I finally stumbled upon and understood internal load. You see early in training, and really at any time in training, two runners can run the same workout and get two different things out of it. While the external load for both of them may have been the same the internal load was not.
A perfect example of this was my friend and I in college. For more than two years we ran most workouts together side by side but I was beating him like 85% of the time. The reason is that I was running more mileage and longer long runs than him so when we went to the track for a workout I was already a little tired from the day before. Each workout was harder internally for me. And by the same token, since I was able to complete the workouts those extra miles that I put in on the weekends paid off during the races. Eventually he figured it out and went on to break my 10k school record by almost a minute, which is good.
I think that the concept of internal load applies to communication and other things as well. The hardest class in my life was just another physics class for a bunch of people. I say something, not meant to be negative or to change a person at all, yet it is taken as negative and derogatory. What is expressed is taken differently by different people. While Mr. Canova doesn't write on this LetsRun thread the person correctly understands the concept. A summary of his LetsRun posts are on this amazing thread, which has stuff copied and pasted from his book.
The concept of internal load is an interesting one. A very valid idea, but something that I really didn't understand enough to name until only a few months ago.