Preventing Running Injuries – the latest research.

The Science of Running

Running Form
Three new studies add some data to the ongoing debate about shoes and running form:

1. Rearfoot vs. forefoot: Harvard anthropologist Daniel Lieberman tested his theories about the best way to run by carefully monitoring members of the university’s cross-country team between 2006 and 2011. The results, published in Medicine & Science in Sports & Exercise, showed that three quarters of the runners suffered a moderate or severe injury each year – and heel strikers were roughly twice as likely to get repetitive stress injuries compared to forefoot strikers. Barefoot runners often cite the shift to forefoot landing as one of the key benefits of ditching shoes, but it’s important to note that all the runners in this study were wearing shoes. The message, Lieberman concludes, is that your injury risk probably depends more on how you run than what you’re wearing on your feet.

2. The joy of cushioning: Wearing heavy shoes wastes energy when you run – about one per cent for every 100 grams of added weight. But on the flip side, a new University of Colorado study suggests that the cushioning in shoes actually saves energy, since you’d otherwise have to use your leg muscles to absorb the force of landing. By adding and subtracting small lead weights from the feet of barefoot runners and runners wearing lightweight running shoes, the researchers were able to work out that shoe cushioning reduces the energy needed to run by about three to four per cent.

3. Making the switch: While Lieberman’s study simply observed the differences between natural forefoot and heel strikers, a U.S. Army study published in the American Journal of Sports Medicine went a step further and actually taught 10 runners to switch from heel to forefoot landing. All 10 of the subjects were selected because they suffered from compartment syndrome, a painful condition that usually requires surgery to resolve. After six weeks of three-times-per-week form training, they had increased the distance they could run without pain from 1.4K to 4.8K on average – and a year later, most had kept those gains. While it wasn’t a randomized trial, the study represents an important first step in showing that running form can be successfully altered.
So where do these studies leave us? We’re still a long way from getting definitive answers about the best way to run, but more evidence is suggesting that running form matters. A good first step – make sure you’re not overstriding, landing with your foot far in front of your centre of gravity.

Iron boosting
Many runners struggle with low iron stores – they don’t get enough in their food, and they lose iron in sweat and through gastrointestinal bleeding. Female runners are particularly at risk, in part because of iron lost during menstrual bleeding. And a new study from Florida State University, published in the International Journal of Sport Nutrition and Exercise Metabolism, suggests another possible factor: prolonged exercise may hinder iron absorption in the hours following exercise. Researchers found that levels of a hormone called hepcidin, produced in the liver, spiked a few hours after their subjects went for a 60- or 120-minute run, and stayed elevated for up to six hours after. Hepcidin reduces iron levels in the bloodstream, hindering your body’s efforts to store iron. The solution: if you take iron supplements (which you should only do if a blood test has confirmed that your hemoglobin or ferritin levels are low), time it so that you’re not taking them in the hours following hard workouts.

Runners High
You may not experience wild, over-the-top euphoria when you run, but most runners do experience some form of “runner’s high” – a subtle change of mood such as an increased sense of well-being or a decrease of anxiety. The reason, according to University of Arizona anthropologist David Raichlen, is that we’re wired to cover long distances thanks to our evolutionary origins as hunters and gatherers. To test this hypothesis, he and his colleagues compared the brain-chemical response to running of three different groups: humans, dogs and ferrets. The reason for those choices: dogs, like humans, are “cursorial” – they’ve evolved to run long distances. Ferrets, on the other hand, hate prolonged exercise. Instead, they sleep an average of 18 hours a day.
Raichlen measured blood levels of “endocannabinoids,” a type of chemical produced in the body that, like marijuana, produces mood changes. Sure enough, after a 30-minute run, endocannabinoid levels spiked to 2.6 times their pre-run level in humans, and those with the highest levels reported the greatest mood changes. Dogs’ levels spiked even higher, to 3.3 times their pre-run level, but ferrets saw no significant change. Interestingly, a 30-minute walk didn’t cause any increase in mood chemicals in humans, suggesting that evolution really does want you to run.

Smog Protection
No one likes smog alerts, but they’re particularly bad news for runners, who spend lots of time outside, breathing heavily and pulling polluted air deep into their lungs. Once they’re in the lungs, pollution particles cause inflammation and oxidative stress, which is why we get warnings about not exercising outdoors. But aerobic exercise like running fights inflammation and oxidative stress in the body – so is it possible that the net benefits outweigh the risks?
Researchers in Brazil tested this idea by exposing mice to diesel exhaust particles from the tailpipe of city buses; some of the mice ran, while others didn’t. Amazingly, the mice in the running group showed no more signs of pollution damage than the mice in the control group who weren’t exposed to pollution at all. Of course, it’s a big leap from mice to humans – these results don’t mean that we’re immune to the effects of air pollution. In all cases, in you can choose to run along a bike path away from traffic and protected by trees, take that option. But if you’re choosing between running on a polluted day and not exercising at all, this study offers an argument in favour of lacing up your running shoes.

Alex Hutchinson is a senior editor at Canadian Running.