A tempo run is a balancing act. The challenge that a tempo run demands is simple: find the fastest pace you can run with the least effort. The best description of the effort is an oxymoron. You go "comfortably hard."
Some more tough-minded folk try to take the art out of tempo running by linking it to heart rate (160 or so) or certain physiological thresholds in the body (the favorite here is lactic threshold, but sometimes aerobic threshold is mentioned), or even a pace: 10 mile race pace is a favorite. But the tempo run does not denote a concrete object or measurable event that takes place in the body. The tempo run is a discipline. Tempo is an art of balancing pace with effort.
It is precisely for this reason that the tempo run is the most important workout that a runner can do. The tempo teaches you to pay attention. A runner can do one of two things when approaching the paradoxical state of comfortably hard. There are two ways to keep the effort from spinning out of control.
The most straightforward thing to do is to slow down--to modulate pace. But there is a different technique. Mastery of this skill is what separates the best runners from the rest. The skill is one of maintaining pace while modulating effort.
The discipline that tempo runs train into us is not to give more effort than is necessary. Often, strangely, trying to run fast gets in the way of running fast. So, when the effort begins to spin up out of comfortably hard, the first thing the experienced runner checks is his relaxation. Am I wasting effort? Am I pushing when I could be rolling? Are my arms tight? Did I forget to relax after the last hill? The tempo run is practice making fast easy--convincing the body and the mind not to be frightened of fast paces, and not to convert that fear into wasted energy, exaggerated effort.
I ran a tempo tonight in the dark. It's harder to measure pace in the dark, as the dark throws off visual perception. This blindness is actually an asset for tempo running because it allows you to forget how fast you are running, not to fear the speed, and just concentrate on the effort, on running fast and controlled and easy.
Before the run, as I jogged to the park, I wondered if the 5:40 miles I hoped to run would be hard. They sounded hard. And I was prepared to give an effort. But there in the dark, I just focused on running strong, as fast as I could go without pushing, and the miles fell off: 5:42, 5:38, 5:37, and then grinning to no one in the pitch black, an easy 5:25.
John Dewey writes in Art as Experience that "Art celebrates with peculiar intensity the moments in which the past reinforces the present and in which the future is a quickening of what now is." A tempo run, when done right, qualifies as a sort of intimate art. Not the kind of art that is hung in museums and watched, but art as experience. The tempo run takes legs and heart and body that have been molded in training. It takes the sum of these past experiences and, with peculiar intensity, it produces a brief present in which the accumulated strength and power and grace of one's history as a runner is felt and lived.
This glimpse, this balance, this art portends a future as well--indeed, a quickening of what now is. If I can run this fast, without effort, then...