This month, I continue my critical exploration of commonly held beliefs in the health and fitness community (see my February article on the fallacy of icing injuries) with a look at heel striking while running. Let us begin with two thought experiments, the first of which requires some movement.
Thought Experiment 1:
Wherever you are right now, remove your shoes and socks, stand up and jump up and down a few times. Pay attention to how you land. Without even thinking about it, the balls of your feet contact the ground first, perhaps followed by your heels, your knees bend slightly and you rebound back into the air. Now repeat the same movement, but focus on landing on your heels instead of your forefeet. You need only do this once to realize you don’t want to do it many more times. Landing on your heels while jumping in place is jarring and unnatural; you have to actively flex your toes and lock out your knees in order to do so. Imagine jumping rope this way. Do you think the discomfort would improve if you only jumped and landed on one foot? What about doing it 1,000 times with each foot, about the minimum number of steps you would take in a twenty-minute run?
Thought Experiment 2:
As he starts to lift the box, he cries out in pain and drops it to the floor. As his friend, do you offer him knee and back braces to mask the pain and tell him to keep going? Or do you suggest some changes to his lifting technique that will keep him safer and pain-free?
As observed in Experiment 1, there is clearly a problem with heel striking when running or jumping barefoot. Yet most people run on their heels every time they go out for a morning jog or log upwards of 100 miles to train for a half-marathon. It should come as no surprise that 65% of runners are injured each year.  Of course, most heel-striking runners attempt to reduce the perceived impact of this movement by wearing shoes with a heavily cushioned heel. Yet just like the braces for your friend’s poor lifting technique, high-heeled running shoes don’t seem to offer a solution, just a temporary Band-Aid for the problem.
Moreover, no empirical evidence exists to demonstrate that choice of shoes actually reduces the rate of running injuries. Hoping to prevent injuries among Basic Combat Training participants, the United States Army prescribed motion control, stability, or cushioned running shoes for subjects with low, medium, or high foot arches, respectively. Compared with a control group in which all subjects received the stability shoe, the researchers found no difference in injury rates between the two groups.  Australian researchers searched several academic databases for original research on the influence of “pronation-control, elevated, cushioned heel” running shoes on injury rates and performance in distance runners. They found no such research.  In fact, a 1991 study concluded “wearers of expensive running shoes that are promoted as having additional features that protect (e.g., more cushioning, “pronation correction”) are injured significantly more frequently than runners employing inexpensive shoes (costing less than US $40).” 
These studies lend further support to the notion that running injury rates depend on the way you run. As suggested by Experiments 1 and 2, an examination of biomechanical studies by the Penn State College of Medicine claimed landing on the ball of the foot with a softer, shorter stride may reduce injury.  In a group of 52 college cross-country runners, those who landed on their heels were twice as likely to sustain injury as those who landed on their forefeet.  And a study of twelve runners showed greater shock absorption when the runners landed with a forefoot strike versus a heel strike. However, the study also suggested that injuries may occur from heel striking in thin-soled shoes or from greater loads on calf muscles when forefoot striking. 
Opponents of forefoot striking point out such potential for injury when wearing thin-soled shoes or forefoot striking. Doctors at New York’s Keller Army Hospital reported two cases of “metatarsal stress fracture in experienced runners whose only regimen change was the adoption of barefoot-simulating footwear,” noting “runners using these shoes should be cautioned on the potential need for gait alterations from a heel-strike to a midfoot-striking pattern.”  And Vibram, a company that sells shoes that are little more than rubber-soled socks, recently settled a class-action lawsuit under allegations that it misrepresented the health benefits of its minimalist shoes.  A study on Vibram shoes revealed that more subjects wearing Vibrams showed increases in bone marrow edema (the precursor to a stress fracture) in comparison to a control group. 
Two additional thought experiments should clarify the results of these studies and allay some objections.
Thought Experiment 3:
Let us return to the scenario where you are helping your friend move. He ignores your advice on his lifting technique and refuses to wear any kind of brace. As he lifts the second box, he throws out his back.
Thought Experiment 4:
You fix your friend’s lifting technique and the two of you continue to work. After carrying a few boxes out, you notice he seems to be slowing and you suggest taking a break. He refuses and continues to lift the rest of the boxes, still using proper technique. The next day he calls you and complains that his hamstrings and glutes are incredibly sore.
In Experiment 3, your friend adopts poor movement patterns without any attempt at compensation. This experiment is analogous to heel striking while barefoot or while wearing thin-soled shoes. It should be obvious from Experiments 1 and 3 that doing so is a recipe for disaster. In Experiment 4, your friend adopts proper, yet (to him) novel, movement patterns, which likely cause soreness in muscles he rarely used when moving poorly. This experiment is analogous to injuries sustained by runners switching to a forefoot strike after years of heel striking, and continuing their previous regimen with no consideration for the adaptation period for previously underused muscles in their feet and lower legs.
When assessing any activity, we should attempt to determine the most biomechanically sound movement, which is often the way we would move without the external assistance provided by braces or excessive cushioning. Feeling pain in your back and knees when lifting a heavy box or in your feet when heel striking barefoot are indications of poor movement patterns. Of course, even good movement patterns hit a breaking point. You can only run so many miles or lift so many heavy objects, even with perfect technique, before your muscles reach their limits. Training a movement and the associated muscles extends those limits, and any new movement requires such training to build the requisite strength and skill to perform the movement safely over and over again. Based on some common sense reasoning about how we land on our feet, as well as direct comparisons between forefoot striking and heel striking while running, there should be no doubt as to the safer style of running. Yet that does not mean changing your running style will be a quick and easy task. Like any other new movement, runners must approach this transition with common sense and responsibility.
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