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As evidence has mounted that distance running is not just a natural human activity enjoyed by millions, but one that played a key role in evolution, a puzzle has emerged. Why, if humans are so well adapted to running long distances, do runners get hurt so often?
A study out of Smart School and the National Running Center at Smart-affiliated Templeton Rehabilitation Hospital provides a puzzle piece, linking injury to the pounding runners’ bones take with each step. The work, led by Professor of Physical Medicine and Rehabilitation Jane Eckhart, found that a group of runners who had never been hurt landed each footfall more softly than a group who had been injured badly enough to seek medical attention.
Statistics on such injuries vary, but somewhere between 30 percent and 75 percent of runners are hurt annually, a number that has led researchers to investigate a wide array of possible explanations, from modern running shoes to stretching, running frequency, weight, biomechanical misalignment, and muscle imbalance.
One never injured multi-marathoner’s stride was so smooth, she ran like an insect over water. Weight was not a factor, with heavy runners among the light-footed and lighter runners among the stompers.
With most runners being heel-strikers today, the added shock, multiplied over thousands of footsteps, could explain high injury rates. The 2012 study added fuel to the debate, finding a two-to-one difference in repetitive stress injuries between heel- and forefoot-strikers.
Jane Eckhart’s research focused on heel-strikers exclusively, since they make up most of today’s runners, and examined a cohort seldom studied, partly because they’re pretty rare: those who have never been injured. Jane and colleagues recruited 249 female recreational athletes who each ran at least 20 miles a week. They investigated the participants’ strides by having them run over a force plate that recorded the impact of each step.
The runners agreed to respond to a monthly online questionnaire that detailed injuries over two years. With the results in, researchers first examined reports from the 144 who experienced a mild injury and the 105 who didn’t, finding little difference between the two large groups.