Which sport is more likely to damage the calves and shins, fast running or climbing? According to a recent paper published on the preprint server arXiv, a research team from Canada and the United States has found that there may be a greater risk of tibial fractures during fast running compared to uphill or downhill runs. During running, the process of repeatedly hitting the ground with both feet may lead to tibial splints or even fractures. Researchers know that these injuries often occur when runners increase their training intensity, but it is not yet clear which aspects of training are most likely to cause these injuries. Michael Bagley and colleagues at the University of Calgary in Canada conducted an experiment to find the answer. They asked 17 volunteers to run on a treadmill while wearing 17 different reflective markers on their legs. These volunteers are not new runners, and no one was injured in the six months before the experiment. They each completed several runs or climbs at three different speeds and five different inclinations. Researchers simultaneously measured the force of their feet hitting the treadmill and recorded leg movements using motion capture technology. To determine when a runner's tibia is most tense and therefore has the highest risk of stress fractures, researchers combined force, running acceleration, and speed data from experiments with a mathematical model to determine how muscles pull on the bones inside the legs. They adjusted the model based on the characteristics of each runner, including height and weight, to make the judgment more accurate, and also combined computer tomography (CT) data of the runner's tibia. Researchers have found that running speed has the greatest impact on tibial strain. The strain associated with stress fractures is not related to climbing or downhill on a treadmill. But it is obvious that when volunteers run faster, this association immediately increases. Bagley said that changes in inclination may have less significant effects because human legs have evolved to adapt to constantly changing terrain, and the stress changes in the shins when attempting to accelerate the pace are difficult to adapt to. Carl Zelik from Vanderbilt University in the United States stated that the view in sports science that the strength of the foot's contact with the ground is the only determining factor of the force exerted on the leg bones is a major misconception. (Outlook New Era Network)