Walk, don’t run or run, don’t walk?

Headline 1 appeared April 5 in the Guardian: “Brisk walk healthier than running - scientists.”

Headline 2 ran in Health magazine the very same day: “Want to lose weight?

Then run, don’t walk: Study.”

Here’s the kicker: Both articles described the same research, 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 data 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 do 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 body mass index (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.

EITHER/OR

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. The incidence of shin splints seemed to be increasing, along with heel spurs, stress fractures and inflammations of the knee.

In the summer of 1984, 52-year-old best-selling author and running guru Jim Fixx died in his jogging shorts, having had a massive heart attack after ignoring his family history of heart disease. 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 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.

GUIDELINES EVOLVE

But mainstream researchers in the field of exercise were a little slower to buy in. Government standards for physical activity, based on advice from the American College of Sports Medicine, still favored more vigorous activities such as running. It prescribed at least half an hour of heavy exercise at least three times per week. “I wrote the guidelines, and I still hold to them,” said Michael Pollock, a prominent exercise physiologist, in the middle of the walking hype.

The debate in academia would last for almost a decade.

Finally, in the mid-1990s, government agencies softened in deference to the power walkers. Americans were advised to do at least half an hour of something less intense than running - a brisk 4- or 5-mph promenade, for example - but they were advised to do this lighter work more often. In other words, their total dose of exercise would be the same, but they would be taking it in a less concentrated form.

The current version of the guidelines makes this logic more explicit. The Centers for Disease Control and Prevention equalizes workouts of varying intensities according to a standard exchange rate of 2-to-1: Every two minutes we spend hoofing around in Rockport ProWalkers equates to a single minute spent on the jogging trail. That means people can mix and match their workouts until they approximate a recommended weekly total: either 75 minutes of sweaty, vigorous workouts, or a double helping (150 minutes) of something moderate - or any custom combination of the two.