Have you ever wondered why your standard “jogging” pace is what it is?
Every runner has a natural running pace. It’s the pace you fall into automatically when you go for your typical moderate, steady run of a certain predetermined distance or duration — five miles, 45 minutes or whatever (a format that probably accounts for 90 percent of all runs performed daily by the worldwide population of runners).
For each runner this pace changes over time as fitness is gained or lost, and it even changes from day to day based on how one feels — a factor that is influenced by fatigue from preceding training, above all.
What determines a runner’s natural running pace? Exercise scientists have made few efforts to answer this question, and the few answers that have been proposed are unsatisfactory. In a 2001 study, researchers from the University of Udine, Italy, tested the hypothesis that natural running pace is determined by the blood lactate level. They expected to find that natural running pace would correspond to the maximal lactate steady state, or the fastest pace a runner could sustain without lactate accumulating to a concentration that would cause fatigue.
Eight recreational runners were first tested for their lactate threshold speed and heart rate, and were then asked to run for one hour at their natural pace. On average, the runners completed the one-hour run at approximately their maximal lactate steady state; however, while there was a lot of variation in the individual lactate steady state speeds among the eight subjects (some were much faster than others, for example), there was significantly less variation in pace levels maintained in the one-hour run, a finding that led the study’s authors to conclude that “besides the need of avoiding lactate accumulation in blood, other factors must be involved in the choice of speed in running.”
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There were two problems with the University of Udine researchers’ lactate-based hypothesis. First, there is no evidence that running pace is strictly limited by blood lactate levels. In short races, for example, runners routinely achieve blood lactate levels that exceed the lactate threshold value. If such high lactate concentrations are “allowed” in short races, how could they impose an immovable ceiling on running pace in other circumstances? The second problem with the lactate hypothesis is that there is no mechanism whereby blood lactate could regulate running pace even if it did cause muscle fatigue. If blood lactate did regulate running pace throughout exercise prior to fatigue, then each runner would run the same pace in every run — the pace corresponding to the “right” blood lactate level.
What the University of Udine researchers were forgetting, and what almost all exercise physiologists forgot in all of their work until sometime after 2001, was the role of the brain in exercise regulation. It is the brain that tells the muscles how hard to work — in this case, how fast to run — during all exercise situations. Therefore, the true explanation of the natural running pace phenomenon must be seated in the brain.