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The members of Harvard University’s men’s and women’s distance running squads are young, fast, fit, skinny, bright, disciplined and, without exception, dutiful. Every day during the cross-country and track seasons, they enter their mileage and pace into an online training Web site overseen by the team’s coaches and trainers.

They also, like most serious runners, get hurt with distressing frequency, often missing practice due to aching muscles or over-stressed bones. Each of those injuries, no matter how niggling, also gets duly reported and entered into the computer.

Meaning that these student athletes, in their high-achieving way, fashioned an excellent database through which to examine running-related injuries, as evidenced by a study published online last month in Medicine & Science in Sports & Exercise.

The study, for which researchers combed through four years’ worth of data about the Harvard runners, has produced the surprisingly controversial finding that how a person runs may affect whether he or she winds up hurt.

Running injuries are a topic of considerable interest to scientists in many disciplines, from biomechanics to evolutionary biology, as well as, of course, to runners. By most estimates, more than half of all runners, whether male or female, collegiate or long past, become injured every year.

But no one knows why so many runners get hurt, although a number of theories have been advanced, including the possibility that hard asphalt roads, lousy Western diets, too many miles, too few miles or high-tech running shoes cause or contribute to the problem.

But Adam I. Daoud, a graduate student in the Skeletal Biology Laboratory at Harvard and the lab’s director, Daniel Lieberman, an evolutionary biologist who co-wrote an influential 2004 paper suggesting that distance running guided the evolution of early man — with better runners earning more food and sex than plodders and passing along their genes — wondered if something simpler might be at work. They wondered whether how your foot hits the ground affects your injury risk.

Most of us who run nowadays strike the ground first with our heels, a pattern promoted by today’s well-cushioned running shoes. There’s suggestive evidence, however, including from Dr. Lieberman’s work, that early, unshod hunter-gatherers landed first on the balls of their feet. So, in recent years, some runners have decided that forefoot striking must be more “natural” and less likely to cause injuries.

But there has been no science to support that idea.

To look into the issue, Mr. Daoud, who had been on the cross-country team as an undergraduate, and Dr. Lieberman not only gained access to the team’s training database, they also gathered the team members and videotaped them.

No one is always a forefoot striker or a heel striker. Your form depends on many factors, including your speed, the terrain, whether you’re tired and so on. But most of us have a predominant strike pattern, and so it was with the 52 Harvard runners. Thirty-six, or 69 percent of them, were heel strikers, while 16, or 31 percent, were forefoot strikers. The proportions were similar regardless of gender.

More interesting was the distribution of injuries. About two-thirds of the group wound up hurt seriously enough each year to miss two or more training days. But the heel strikers were much more prone to injury, with a twofold greater risk than the forefoot strikers.

This finding, the first to associate heel striking with injury, is likely to fuel the continuing and not-always civil debate about whether barefoot running is better. (It hurts to hit the ground with your heel if you’re not wearing shoes.) But both Dr. Lieberman and Mr. Daoud, now a medical student at Stanford University, are quick to point out that their study did not in any way address the merits of going barefoot.

All of the Harvard runners wore shoes, and most, as Dr. Lieberman says, “wore different shoes every day of the week.” Some ran in well-cushioned shoes and became injured, while others did not. Likewise for those who usually ran in minimal racing flats. Some got hurt; some did not. And forefoot striking, over all, was not a panacea. Many of the forefoot strikers were felled by injuries.

But in general, those runners who landed on their heels were considerably more likely to get hurt, often multiple times during a year.

Does this mean that those of us who habitually heel-strike, as I do, should change our form? “If you’re not getting hurt,” Dr. Lieberman says, “then absolutely not. If it’s not broke, don’t fix it.”

But, says Mr. Daoud, who was himself an oft-injured heel-striker during his cross-country racing days, “if you have experienced injury after injury and you’re a heel-striker, it might be worth considering a change.” (If you’re unsure of your strike pattern, have a friend videotape you from the side as you run, he suggests, then use slow motion to watch how your foot hits the ground.)

If you do decide to reshape your stride, proceed slowly, he cautions. Many people who abruptly switch to barefoot running or a forefoot running form get hurt in the process, he says. The body’s tissues adapt to the forces generated by long-term heel striking. Change your form, and the forces will affect different parts of the leg, leading to soreness and, potentially, injury.

Try landing on the ball of your foot “for five minutes at first at the end of a run,” Mr. Daoud suggests. Work up to longer periods of forefoot landings as your body adjusts and only if you do not notice significant, continuing soreness.

In his own case, Mr. Daoud now runs consistently with a forefoot landing style, but the transition was not seamless. “I broke a metatarsal while running my first marathon after transitioning a bit too quickly and expecting a bit too much from my body too soon,” he says. So fair warning to those considering making the transition to forefoot landings: “Give your body time!”