A new study suggests we naturally run with as little muscle activation as possible.
Written by: Matt Fitzgerald
On May 7, 2005, Galen Rupp set an American junior record of 28:25.52 for 10,000 meters. He was one day shy of his 19th birthday at the time and had only been running seriously for a few years. Six years later, Rupp set a new American record of 26:48.00 in the same event.
How did Rupp improve his 10,000m time by 97 seconds in early adulthood? What were the physiological changes underlying his tremendous gains in performance? You might assume it was a strengthening of his aerobic system, measurable as an increase in his VO2max. After all, running is an aerobic sport, and nothing aids running performance like a strong aerobic system. Nevertheless, your assumption is probably incorrect.
Rupp’s breakthrough can be tied to inherent laziness–and I don’t mean that he didn’t work hard to achieve his big breakthrough. Let me explain.
Strengthening of the aerobic system certainly is the most important factor in performance improvement in the first few years of a runner’s career. The heart becomes bigger and more powerful, the blood becomes thicker, the muscles become more densely packed with capillaries, aerobic enzymes, and mitochondria, and so forth. When sedentary individuals are subjected to regular aerobic exercise, their VO2max typically increases by upwards of 15 percent in a matter of two or three months.
This pattern does not continue, however. After two or three years of training and competing, serious runners see only minimal gains in aerobic power. By then the heart has gotten as big and strong as it can get, the blood as thick as it will ever be, and the muscles as densely packed with capillaries, aerobic enzymes, and mitochondria as they possibly can. Yet serious runners may continue to improve markedly after their first two or three years in the sport, as Galen Rupp did.
So if it wasn’t continued strengthening of his aerobic system that enabled Rupp to make his leap forward as a runner, what was it? The best evidence suggests that while aerobic development peters out after a few years, improvements in the efficiency of the running stride continue long afterward. It is these improvements that enable serious runners to set big PRs after their first few years in the sport.
It has been proposed that runners naturally and unconsciously tend to adopt a stride pattern that minimizes the energy cost of running given their body structure. For example, when runners are asked to slightly increase or decrease the length of their stride in a laboratory setting, they always become less economical. Thus it appears that runners find the stride length that minimizes the energy cost of their running without ever thinking about it.
This does not mean every runner starts off running as economically as he possibly can from his very first day in the sport, however. While beginners may dial in cruder variables such as stride length fairly quickly, there are a million other subtler nuances of the stride that are gradually refined and made more efficient over weeks, months, and years.
Researchers at the University of Massachusetts recently created a computer model that was designed to determine whether the body seeks to minimize energy cost directly when running, or whether it seeks some other objective and energy cost just happens to be minimized as a result. These researchers took biomechanical measurements from a bunch of runners and compared them to three different computer simulations of running. In one of these simulations, virtual runners were made to run for minimum energy cost directly. In a second simulation these same virtual runners were made to run in the manner that minimized total muscle activation. And in the third they ran to minimize muscle stress. As it turned out, the simulation in which the virtual runners ran to minimize muscle activation most closely matched the way the real runners in the study actually ran.
If these findings are valid, then they suggest that some sort of control mechanism in the brain is able to detect the amount of muscle activation that is required to run at various speeds and automatically latches on to stride patterns that reduce muscle activation at each speed. It’s a self-serving capability based on the principle of laziness. Our bodies really don’t want us to run, but we make them. Our bodies deal with being forced to run by constantly searching for and finding ways to run with less and less muscle activation. Ironically, it is this hardwired laziness that runners like Galen Rupp have to thank for major performance breakthroughs that come after their aerobic systems are already as strong as they will ever be.
About The Author:
Matt Fitzgerald is the author of Iron War: Dave Scott, Mark Allen & The Greatest Race Ever Run (VeloPress 2011) and a Coach and Training Intelligence Specialist for PEAR Sports. Find out more at mattfizgerald.org.