Runners may face a greater risk of developing fractures in their shin bones when they run quickly, compared with when they run uphill or downhill.
The repetitive pounding motion of running can lead to painful overuse injuries known as 鈥溾�� and even fractures in runners鈥� shin bones. Researchers know that these fractures often happen when runners increase the intensity of their training, but it isn鈥檛 well understood which aspects of training are most likely to cause these injuries. at the University of Calgary in Canada and his colleagues set up an experiment to find out.
They asked 17 volunteers to run on a treadmill while each wearing 17 different reflective markers on their legs. No volunteer had been injured in the six months before the experiment and none were beginner runners. Each of them completed several runs, at three different speeds and five different inclinations, while the researchers measured the force of their feet hitting the treadmill and used motion capture technology to record the movements of their legs.
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To determine when runners鈥� shin bones were most strained, and therefore at greatest risk of stress fractures, the researchers combined the force, running acceleration and speed data from these experiments with a mathematical model for how muscles pull on bones inside of the leg. Baggaley says they made these determinations more precise by adjusting the model for each runner鈥檚 characteristics, including height and weight. They also incorporated information from past work with computerised tomography (CT) scans of the volunteers鈥� shin bones.
Across experiments, the researchers found that running speed had the most impact on shin straining. 鈥淲e didn鈥檛 see a difference in the strains which we believe are associated with stress fracture development when you run uphill or downhill. But it was obvious that when volunteers ran faster, these strains increased quite a bit,鈥� says Baggaley. He says that changes in inclination may have a less pronounced effect because human legs evolved to adjust to changing terrain and naturally compensate for the strains better than when a person is trying to increase their pace.
The idea that how hard your foot hits the ground is the only determiner of how much force your leg bones experience has been a big misconception in sport science, says at Vanderbilt University in Tennessee. Models like the one used in the new study are now filling in key knowledge gaps about what actually happens to our bones when we run under different conditions.
Baggaley says that though there are other factors that may contribute to shin bone fractures, such as malnutrition or past bone injuries, there is a clear takeaway from this research: slower is better for anyone worried about their shins.
arXiv
