Einstein had nothing on runners. Oh, he might have come up with that E=mc2 thing, whatever that's worth. But runners couldn't care less about energy equaling mass times the speed of light. We're more concerned with our lack of energy if our mass expands and produces the speed of fright.

We need more-practical ideas. More-useful stuff. That's why I've come up with twin theories to keep facts from interfering with results.

The first, the Theory of Running Relativity, is needed when we discover A2=ST,SOG! (Advancing Age equals Slower Times, Son Of a Gun!). Nothing boosts motivation like discovering times are relative.

The same ingenuity that has given us waffle-soled shoes and high- altitude sleeping tents has blest us with age-equivalent performance tables. These calculations aid those of us who aren't bursting with enthusiasm to run slower times as we get older. They take into account your age and present race performance, then determine a comparable time if you'd run the race at a younger age.

What a concept! I can be better than I've ever been O relatively. I may be getting older and slower, losing my hair and flexibility, and have a decreasing maximum heart rate, but with the Theory of Running Relativity I'm actually the best I have ever been.

Information like this keeps me showing up at the starting line. What better motivation than to discover that with my current 10K time, I could kick my own butt of yesteryear? I can psyche myself up before races by trash talking at old photographs of myself. Clearly that's the epitome of competing against oneself.

Runners have more than age-based relativity. We also have tables that tell us, based on our present time at one distance, what time we should run another distance. Take our half-marathon time and determine, theoretically, what we should do right now in a 5K.

Life should be so predictable. Plug in the fact it took 43 minutes to travel 27 miles to the airport during morning rush-hour traffic, then be able to determine how long the drive should take if done mid-day, in a strong rain, with construction eliminating two lanes of the three-lane highway for a 4.5-mile stretch. That's useful information to have.

Here's where theory two, the Runners Theory of Rationalization, comes into play.

I recall being disheartened when I couldn't meet my theoretically- equivalent marathon time based on my 10K time. I thought maybe I wasn't pushing myself hard enough in the marathon. Maybe I was starting out too fast, or wasn't refueling enough or tapering correctly.

Theory two made it clear my running shoe wasn't half-empty, it was half- full. I decided I wasn't underachieving in the marathon; I was overachieving in the 10K! (I can't race with the leaders, but I can rationalize with the best.)

Poor times at some races only magnified the overachieving brilliance of my efforts at other races. The worse I did here, the better I was there. I could never fail!

This theory goes beyond running too. The fact I could never get a souffle to rise really means I've transcended my natural culinary talents getting breadcrumbs to stick to my eggplant parmigiana. My inability to make origami paper swans actually means I'm overachieving when I make paper airplanes that fly more than seven feet

Einstein can have his old postulate about physical laws of nature. We've got our own physical laws of running with the twin theories to help us interpret today's performances as better than yesterday's, but not as good as tomorrow's.

We've got the ingenuity. We've got the resources. We're willing to do whatever it takes for the best of times.

Excerpted by permission from I Run, Therefore I Am -- Nuts! by Bob Schwartz. Copyright (c) 2001 by Human Kinetics Publishers, Inc. Available at bookstores, Amazon.com, humankinetics.com or 1-800- 747-4457.