THE BOSTON MARATHON IS TOMORROW. Along with the N.Y. Marathon, these are two events that I try not to miss. Top notch runners are the most elite athletes around. It makes me laugh to see a baseball player leg out a double and then stand there on second base huffing and puffing. Trained marathoners pull off five-minute miles, mile after mile, often going faster at the end than at the start. Aside from the physical stamina and strength it takes, there is a significant mental element to run in these events. I’m not only referring to the mind-over-matter aspect of strenuous physical activity alone. Each runner is trying to determine how best to deal with his competitors, when to speed up, when to force the pace, when to attempt to break from the pack. The race commentators read the signs of the effort each runner is putting out, the relative posture, the motion of the arms, the expression on the face, the overt evidence of how tired or hurting an individual runner appears to be. It is hard to imagine what a marathoner goes through during a race, and it is equally difficult to appreciate the exultation one feels crossing the finish line.