Random item from my box of running memorabilia.

Wednesday, March 14, 2012

A False Alarm About Landing on Your Heels

       Some recent research has revived a very old issue among runners--whether you should land on your heels (as in fact most of us distance runners do) or on the balls of your feet (forefeet) as most sprinters and top middle-distance runners do.  The new research, reported by the Harvard professor of human biological evolution Daniel Lieberman and his colleagues, has raised a ruckus and caused a lot of consternation by suggesting that runners who land on their heels may be at greater risk of injury than those who land on their forefeet.
       I have good reason to think that for the great majority of runners, that conclusion might be mistaken.  I'm not challenging Lieberman's study at all, and in fact I think Lieberman is one of the most important figures in the science of human biomechanics.  So, how could the injury-risk worry be a mistake?  A simple answer is that unless you are a college-level cross-country runner or elite competitor at sprints or middle-distances, the study may not apply to you--and in fact its findings may be the opposite of what they'd be for you and me.
       Here's why.
       Of the approximately 50 million Americans (according to surveys by the Sporting Goods Manufacturers Association) who are active lifestyle runners or joggers, I'd bet that more than 95 percent are either (1) middle-of-the-pack road or trail runners (those at the back of the pack still get to call themselves "middle-of-the-pack") who run distances ranging from 5k to half-marathons, or (2) long-distance runners whose main interests range from half-marathons to marathons or ultras.  People in those two categories are mostly runners who have a natural inclination to land on their heels.  And for most, to land on their forefeet would feel so unnatural to them that few would even try it.
       To illustrate this point, before going on to explain why heel-striking probably does not increase injury risk, consider the case of Clarence deMar, the legendary Boston Marathon runner of a century ago.  In his 1937 memoir, Marathon, DeMar tells of how he began his running career by going out for cross-country in his third year of college:  "At that first trial . . . captain Stevens kept yelling at me, 'Run on your toes, on your toes!'"  DeMar tried it, but "I couldn't get the idea of hitting the toes first.... Sometime within a year I learned how to run on my toes.  Still, I have never done that any more than one third of the time."  Staying mainly on his heels, DeMar went on to win the Boston Marathon seven times.  And considering how little was known about exercise physiology, optimal training, shoes, nutrition, and endurance fueling at the time, his sub-2:20 marathons would probably rank him right up there with the top American marathoners of today.
       When I read that "run-on-your-toes" passage in DeMar's memoir, I almost fell out of my chair in surprise: the same thing had happened to me, half a century after it happened to him!  When I went out for cross-country as a high-school sophomore in 1956, my coach took one look at me and shouted, "Run on your toes! Run on your toes!"  I, too, learned to do it, and as it turned out I was quite successful at cross-country; the following year, I broke the Westfield (N.J.) High School course record that had been set by Westfield's New Jersey state champion Edgar Hoos ten years earlier.  And I ran fairly well in college as well.  But--keep this in mind--it was in cross-country that I received and followed that "run-on-your-toes" admonition, as it was for DeMar and, no doubt, thousands of others.  I'll come back to this cross-country connection in a minute.
       A few years after my graduation from college, in the mid-1960s, I decided to run a marathon.  I entered the Cherry Tree Marathon in New York City (a predecessor of the New York Marathon), and at around 17 miles into the race found myself catching up with a man I knew to be a legend in the New York running community--Ted Corbitt.  Ted had run the marathon for the U.S. in the 1952 Olympics, and had been the national champion in 1954.  He'd also been the founding president of the New York Road Runners Club, and first president of the Road Runners Club of America.  He was older now, and not as fast as he'd once been, but I could hardly believe I was catching him.  As I pulled alongside, Ted glanced at my feet and smiled, and said, "You know, you might run easier if you let yourself land on your heels."  It was as if I'd been spoken to by God.  I took what he'd said to heart, and over the next several months I let myself gradually return to the way I'd landed on my feet before that first day of high-school cross country.  My feet, ankles, legs, and back all became more relaxed, and ever since, I've felt more in touch--well, I have been more in touch--with the ground I was running on.  Years later, I would surmise that that quiet suggestion from Ted Corbitt had added 20 miles to my running longevity (I'm now in my 55th consecutive year).
       Then, last month, the study reported by Professor Lieberman and his colleagues at Harvard hit the news.  What they found was that over a four-year span, Harvard cross-country runners who landed on their heels had higher rates of injury than those who landed on their forefeet--the very opposite of what my own experience had suggested.  The result seemed counterintuitive, because in short events, from 100 meters to 5000 meters or so, where most top runners do land on their forefeet, the greater speed and longer strides required for success in those races require greater biomechanical force, which puts greater stress on the legs and feet.  In the slower, longer, distance events, most of us land on our heels--exerting less force and therefore presumably making ourselves less vulnerable to injury than we'd be if we ran like sprinters or 5000-meter runners.
       The Harvard study seemed to belie my Ted Corbitt epiphany, but I think I might have an explanation.  That study's results were for cross-country, which is run at neither very-short (primarily forefoot) nor very-long (primarily heel-strike) distances.  At the college level, cross-country races are run at in-between distances, around 10,000 meters, where both heel-strikers and forefoot strikers can be competititive--and where of course both were represented on the Harvard men's and women's teams.  But--here's the rub--the training for cross-country requires a lot of interval work, or other high-speed running.  Those of the Harvard runners who were naturally inclined to run on their heels may therefore have been farther out of their element--pushing the envelope, biomechanically--than were the natural forefoot strikers.  The stresses on feet and knees were therefore relatively greater for the heel strikers than for their forefoot-striking teammates, so their vulnerability to injury at those speeds was greater.  I suspect that if the same group of runners had been training for marathons or ultras, with much less speedwork but greater mileage, it would have been the forefoot strikers who were more out of their element--and the injury results might well have been reversed.
       That explanation might beg the question of why long-distance runners shouldn't (or don't) take advantage of the greater power that can be deployed by running on their forefeet, just as sprinters or milers (or about a third of the Harvard cross-country runners) do.  The answer is suggested by another study of the heel-vs-forefoot question (reported by David Carrier, the University of Utah persistence-running theorist), which found that while heel-striking is slower, it is about 55 percent more energy-efficient than running on the forefeet.  In shorter-distance foot races, just as in short-distance car races, energy efficiency offers no competitive advantage.  If a drag-race driver knew he had the fastest car, it wouldn't matter to him if the car were so energy-squandering that it got only 2 miles to the gallon.  Only its power and speed would matter.  Similarly, if a sprinter or 800-meter runner gets only two-thirds the distance per 100 calories of fuel that a heel-striker gets, it doesn't matter.  But for a marathoner or ultrarunner, it matters hugely.  Sprinters have to run on their forefeet to maximize their power.  Most ultrarunners land on their heels to maximize their staying power.  Clarence DeMar, it seems, knew this all along.  Reflecting years later on that "run-on-your-toes" exhortation, he mused that forefoot running "seems to me a trifle faster, but it is more fatiguing."
       I had been a good cross-country runner in high school and college, but at the Cherry Tree Marathon I was a prime candidate to learn how much more easily and sustainably I could run this much longer distance--and eventually run even farther--by reducing the force of my footplant.  Ted Corbitt, who a few years earlier had been the national marathon champ and the best ultrarunner in the country, knew that at a glance.