If you're a runner, you might have noticed this surprising headline from the April 5 edition of the Guardian: "Brisk walk healthier than running—scientists." Or maybe you saw this one, which ran in Health magazine the very same day: "Want to lose weight? Then run, don't walk: Study."
Dueling research from rival academic camps? Not exactly. Both articles described the work of a herpetologist-turned-statistician at the Lawrence Berkeley National Laboratory named Paul T. Williams, who, this month, achieved a feat that's exceedingly rare in mainstream science: He used exactly the same dataset to publish two opposing findings.
One of Williams' papers, from the April issue of Medicine & Science in Sports & Exercise shows that habitual runners gain less weight than habitual walkers, when the amount of energy they put into their exercise routines is the same. The other, published in April in Arteriosclerosis, Thrombosis, and Vascular Biology, used a similar analysis to show that running is no better than walking when it comes to the prevention of high blood pressure, high cholesterol, diabetes, and coronary heart disease. So there you have it, and there you don't. Running is better for your health, or perhaps it isn't.
Despite the flip-flop headlines, the findings are not as contradictory as they seem. Losing weight is not the same thing as getting fit—your metabolic health has more to with triglycerides and hypertension than it does with your size in chinos—so there's no fundamental reason why Williams' walkers couldn't gain more weight than the runners while their risk for cardiovascular disease remained the same. The 47,000 people involved in Williams' study were drawn in large part from middle-aged subscribers to exercise magazines who agreed to fill out his surveys, and most of them were slender at the outset. They started with an average BMI in the “normal” range, between 21 and 25. (Overall, middle-aged, U.S. adults have an average BMI of more than 28.) Since the health risks associated with being fat don't kick in until you're very large, they wouldn't necessarily apply to Williams' subjects.
But the deeper story here has more to do with Williams' second finding, that neither form of exercise was any better than the other at promoting cardiovascular health. When Williams set up his gigantic database of avid runners and walkers in the early 1990s, he hoped to help resolve an old debate in exercise science: If you match up workouts according to the amount of energy that they require, are all forms of physical activity created equal? Would a tough and sweaty workout be any better for your health than an easygoing one that lasted twice as long?
Researchers began to ask these questions in the early 1980s, in response to worries over the health effects of jogging. In two decades, the number of self-identified runners in the nation had grown from 100,000 to 30 million, but as the fitness craze expanded, so did concerns about its downsides. Doctors started talking about the natural "endorphin high," and worried that a person might become addicted to certain forms of physical activity. The incidence of shin splints seemed to be increasing, too, along with heel spurs, stress fractures, and inflammations of the knee. Could all this compulsive running be doing more harm than good?
Those fears were realized in the summer of 1984, when the 52-year-old best-selling author and running guru Jim Fixx collapsed dead in his jogging shorts, having had a massive heart attack just 100 yards down the road from his motel. At around the same time, the president of the Rockport shoe company paid a cardiologist named James Rippe to investigate the benefits of walking. Might a less intense form of exercise do the body good? Rippe, who would later write Heart Disease for Dummies and found the Rippe Lifestyle Institute in Orlando, Fla., released some promising data. If you take a swift, half-hour stroll at least three times per week, he said, that should be enough to improve your cardiovascular fitness by 15 percent.
Now the sporting goods industry had a bit of science to support a new and (allegedly) safer form of exercise. By this point, enthusiasm for running was already in sharp decline—the number of joggers in the United States would fall by almost 40 percent between 1979 and 1985—and Rockport led the charge to invent the leisure-time pursuit of "power walking." In the fall of 1984, just a few months after Jim Fixx's death cast a shadow over recreational running, Rockport started selling the ProWalker athletic shoe, the first product in its class.
The trend for walking reached its stride in 1986, with nearly 20 million participants and the inaugural issue of Walking magazine (tagline: "Stop Talking, Start Walking"). This was big business, too: More than 40 companies followed Rockport's lead and released versions of the walking shoe. "If you look at the fitness boom as ripples on a pond, then jogging was the first ring, aerobics the second, and we think walking is the third," said the advertising director for Nike to the Los Angeles Times in 1987.