After five miles at the National Capital 20 Miler about 10 years ago, I discovered, much to my surprise that my legs were not going at a sub-six-minute-per-mile pace any more. Refusing to accept the fact that I was 46 years old and, looking for another excuse, I reasoned that I had started too fast, lost momentum, and then began decelerating. When I realized that approach could only lead to one conclusion--to stop--I decided to hold a slower pace for a longer time, then pick it up at the end. In fact, with three miles to go, I found a second wind (no kin), and began passing people.

What I discovered that day was pacing, and the pleasures thereof.

For years, I had started too fast. In fact, I led the 1979 Marine Corps Marathon at the one-mile mark before the crowd passed me. That was not fun.

More fun is to maintain a steady pace, concentrating on conserving energy and impact with each step, and waiting patiently for the moment when you know for sure you can finish, and then bursting into speed.

Running within yourself avoids the small injuries that occur when you race too soon in a competition. Those small injuries exhaust you late in the race when you alter your stride to avoid exacerbating the sore spots.

Pacing keeps you from going anaerobic-the threshold when your heart rate approaches its maximum and the CO2 level in your bloodstream (the waste product of carbohydrate metabolism, as CH2O + O2 -> H2O + CO2) exceeds your bloodstream's buffering capacity to store CO2, thus causing your bloodstream to store CO2 molecules as lactic acid. Keep below the lactate threshold, and you can stay fresh throughout the race.

Finally, pacing is fun. Passing people late in a race is a great thrill, especially when they are in your age group. With each person you pass, you move one step closer to winning an award. At Marine Corps Marathon, I keep score after the half-way mark- my best record was in 2005, when I passed 165 in the last half, and only three passed me. Remember that it is a sporting event!

To summarize, why pace?

To guarantee your finish

To minimize the probability of injury

To conserve stored energy

To make the last parts of the race fun instead of effort.

A week after my discovery at the 20-miler, I tried pacing at the old Georgetown Classic 10K. The result was my last-ever sub-36 finish, 35:55, to win my age group and get my photo in the Washington Running Report.

I love it when a plan comes together.