Does running a marathon push the body further than it is meant to go?
The conventional wisdom is that distance running leads to debilitating wear and tear, especially on the joints. But that hasn't stopped runners from flocking to starting lines in record numbers. Last year in the U.S., 4,25,000 marathoners crossed the finish line, an increase of 20 per cent from the beginning of the decade, Running USA says. Injury rates have also climbed, with some studies reporting that 90 per cent of those who train for the 26.2-mile race sustain injuries in the process.
Not inherently risky
Now a best-selling book has reframed the debate about the wisdom of distance running. In “Born to Run”, Christopher McDougall, an avid runner who had been vexed by injuries, explores the Tarahumara Indians of Mexico, a tribe known for running extraordinary distances in nothing but thin-soled sandals. McDougall makes the case that running isn't inherently risky. Instead, he argues that the commercialisation of urban marathons encourages overzealous training, while the promotion of high-tech shoes has led to poor running form and a rash of injuries. Scientific evidence supports the notion that humans evolved to be runners.
Most mammals can sprint faster than humans; having four legs gives them the advantage. But when it comes to long distances, humans can outrun almost any animal. Because we cool by sweating rather than panting, we can stay cool at speeds and distances that would overheat other animals. On a hot day, a human can even outrun a horse in a 26.2-mile marathon.
There is other evidence that evolution favored endurance running. A study in The Journal of Experimental Biology showed that the short toes of the human foot allowed for more efficient running, compared with longer-toed animals. Increasing toe length as little as 20 per cent doubles the mechanical work of the foot. Even the fact that the big toe is straight, rather than to the side, suggests that our feet evolved for running.
Spring-like ligaments and tendons in the feet and legs are crucial for running. A narrow waist and a midsection that can turn allow us to swing our arms and prevent us from zigzagging on the trail. Humans also have a far more developed sense of balance, an advantage that keeps the head stable as we run. And most humans can store about 20 miles' worth of glycogen in their muscles.
And the gluteus maximus, the largest muscle in the human body, is primarily engaged only during running. Your butt is a running muscle; you barely use it when you walk.
Change of biomechanics
So if we're born to run, why are runners so often injured? A combination of factors is likely to play a role, experts say. Exercise early in life can affect the development of tendons and muscles, but many people don't start running until adulthood, so their bodies may not be as well developed for distance. Running on only artificial surfaces and in high-tech shoes can change the biomechanics of running, increasing the risks of injury.
What's the solution? Slower, easier training over a long period would most likely help; so would brief walk breaks, which mimic the behavior of the persistence hunter. And running on a variety of surfaces and in simpler shoes with less cushioning can restore natural running form.
