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"I am so happy that the phenomenon of pacing has become the object of serious scientific exploration lately, after having been almost entirely ignored throughout the history of the discipline of exercise science. Pacing is to me one of the most fascinating phenomena in endurance sports. In any race lasting longer than approximately 20 seconds one must go as fast as one can without going as fast as one can, if you know what I mean. That is a tricky challenge–arguably the single greatest challenge in endurance competition.

And yet this challenge was not only ignored for a century but so overlooked as to scarcely be recognized as existing. I think there are two reasons for this oversight. First, scientists could not see inside the brain, which is obviously the seat of pace regulation. Second, scientists could see inside the rest of the body, and since scientists always exaggerate the importance of what they can see, they came to explain pacing regulation–absurdly–entirely in terms of physiological events occuring below the neck. For example, they presented the argument that lactic acid accumulation prevents runners from sustaining a pace faster than the lactate threshold in marathons, overlooking the simple fact that if lactic acid levels acted as a pace governor in any circumstance then no runner could ever exceed his or her lactate threshold pace regardless of the race distance.

More recently, some curmudgeonly exercise scientists have responded to the new line of research into the pacing phenomenon by dismissing it as “too obvious” to merit such scrutiny. These scientists contend that endurance athletes simply know how far each race is and consciously hold themselves back appropriately instead of being stupid and sprinting their way to a quick and complete bonk from the starting line.

A new study by researchers at the University of Exeter shows how it really is. Eighteen competitive cyclists were divided into two groups, each of which performed a series of four, 4 km cycling time trials separated by 17-minute recovery periods. Both groups were instructed to complete each time trial in the shortest time possible, but members of one group were told the distance of the time trials before starting and were given distance feedback information throughout each trial, whereas members of the second group completed all four time trials blindly, although aware that the distance (whatever it was) of the four time trials was the same.

As you probably could have predicted, in the first time trial members of the blind group were far more conservative than members of the aware group and completed the time trial much more slowly. But with each subsequent repetition of the time trial the blind cyclists went a little faster until, in the fourth and last time trial, the average finish times of the two groups were identical.

These results provide clear evidence that the subconscious brain plays a dominant role in the regulation of pace in race-type efforts. If below-the-neck physiology governed pace, the cyclists in the blind group would not have exhibited a learning effect over the course of the four time trials. Instead they would have performed exactly as the distance-aware cyclists did from the get-go. On the other hand, if pacing were controlled consciously, it is also unlikely that the times of the blind cyclists would have converged with those of the aware cyclists by the fourth time trial, as the blind cyclists had no distance information at their disposal at any time, but had to learn to pace the time trials optimally entirely by feel."

http://mattfitzgerald.org/blog/?p=237