Shoes and running injuries – where are we today?

When Dr. Benno Nigg went into retirement this summer he used the occasion to organize a symposium where many of his companions, but also young researchers discussed the future of running and running shoe research. The "running-symposium" in the Canadian Calgary on 15 and 16 August 2014 thus was not a classical scientific congress, but it offered the option for exchange and determination of where running shoe research is today.

Dr. Benno Nigg

"This conference is different from all the other conferences I know", said Simon Lüthi in the middle of a discussion. He was Benno Nigg's first PhD. student when Nigg changed from the ETH Zürich to the University of Calgary in order to design an interdisciplinary research center there. This research center dealt with the research of human locomotion. A focus of the "Human Performance Laboratory" was: Running and running shoes.

Ten keynote lectures and five panel discussions looked closely at these two topics. Not only recent trends, but also false presumptions from the past were discussed with a frankness that is quite rare.

Benno Nigg himself talked in his lecture once more about the reasons why they did research about running shoes at all. Already in the 70s there had been statistics of a certain percentage of runners that were injured in the course of a season. "Our assumption was," according to Nigg, "that shoes do play a role here and you could lower the injury rate by using corresponding shoe or protection designs." This assumption was supported by first biomechanical measurements that showed a strong impact during the heel-strike and a pronation during the heel-strike phase that appeared unnaturally strong. That was the birth of modern sports shoe research.

Impact and pronation were to dominate research and the concepts of sports shoe producers for years. They still determine today big parts of their product line of many manufacturers. However, in biomechanics these concepts are no longer used. "There is no evidence, neither using an epidemiological nor a prospective study that one of these two could be the reason of injuries," Joe Hamill from the University of Amherst, USA, stated. Various studies had shown that impact forces cannot predict if someone gets injured, Benno Nigg explained. For example the forces in the joints were higher in the push-off phase than in the heel-strike phase. And if impact forces would indeed play a role here, according to Nigg, then faster runners would have to be injured more often, because the impact forces get bigger with speed. But this was not the case.

Also pronation that was intended to be curtailed with shoes for decades, has meanwhile be rehabilitated as a natural cushioning mechanism. This happened at the latest with the study of Rasmus Nielsen from Denmark, who examined the position of feet of 900 runners. His result: You can hardly find runners with a pronation exceeding 10 degrees. And runners with a normal pronation had the fewest injuries within the observation period of one year. "This is exactly the opposite of what we used to believe," Nigg exclaimed. "It looks like pronation is an advantage."

Tracking injuries

After the elimination of the two main suspects, there was the question what other factors are the triggers and why they have not been detected yet. "The field of research has not advanced in the last twenty years. It is time for new ideas," Willem van Mechelen from the University of Amsterdam said. He did his doctorate on the factors leading to running injuries.

For twenty years the parameters that were seen in connection with running injuries had basically remained the same. Only few ones had been added. In the literature different risk factors were suggested, said van Mechelen. But so far only preinjuries were confirmed as risk factors. The studies could not show so far if and how errors in training also had played a role. "But since running injuries are only caused by running training, it is not farfetched that the product of training scope and training intensity has an influence." 

Leaving the lab

"There are many factors for injuries and their interactions are a complicated puzzle that needs to be solved," Willem van Mechelen explained. Researchers are obviously ready to reconsider their present research approaches, measuring methods and statistical evaluations and to complement them with new approaches or to completely replace them.

For decades biomechanic scientists examined single parameters like impact forces, pronation, knee movement or pressure distribution, because they thought they might be the reason for certain injuries. They formulated hypotheses and examined them in experiments or in prospective studies. "We are entering a new era of data and knowledge collection," Matthew Nurse, once a student of Benno Nigg and today head of a research team at Nike, said. In the next decade research would leave the lab. "Research will go to the fields and measure how people train, when they rest and when they are in a contest."

"In the future you will have sensors all over the body that deliver more information on locomotion and bodily strain than the present techniques." Björn Eskofier from the University of Erlangen, Germany, provided an outlook for the possible future of biomechanics. Light, wearable systems, perhaps linked to smart phones or smart watches for data collection and storage, are supposed to collect data of the athlete. ECGs to record heart activity, EMGs to register muscular activities or acceleration recorders and gyroscopes to measure body and joint movements could soon be part of the basic equipment in biomechanic analyses.

This new approach, described as data-driven technologiy or simply "big data", collects data on motions, forces or muscular activities, as comprehensively as possible without formulating classical hypotheses. "We will have many data and therefore need an algorithm for the analysis," Björn Eskofier explained the challenge of this new technique. Traditional statistical methods could not handle so easily these amounts of data. This was similar to marketing, Matthew Nurse explained. "50% of the ad budget is squandered money. But we do not know which 50%. So 50 % of the data that we collect might not be relevant. But this is only found out after the evaluation.”

Björn Eskofier is convinced," Data-driven techniques can provide valuable means for analyses." Thus it was not only possible to process big amounts of data but also several dimensions could be examined at the same time. Instead of following only one hypothesis, especially in the case of the search for causes of injuries, the mathematic algorithm could find connections between individual parameters and thus give new insight how injuries occur. Eskofier countered the objection that this method could hardly distinguish between cause and effect, by explaining that "big data" naturally did not provide evidence, but valuable hints which areas would be worth looking into.

Using comfort to find the right shoe

What does the farewell to the old concepts of cushioning and pronation control mean for the shoe industry? Do we need completely new shoe concepts or is it merely important that every athlete finds the shoe that suits him out of a choice that is as wide as possible? Most participants of the symposium could affirm that statement. "It is not a matter of right or wrong," Simon Lüthi said. "The consumer needs a broad range where he finds what he needs." For the industry it is important to know which range to provide.

But how does an athlete select the right shoe ? According to Benno Nigg, he should go by his notion of comfort. Comfort, Nigg says, is a good indicator for the avoidance of pain caused by the shoe.

by Wolfgang Best

Read more about the running symposium in the next issue of foot&shoe (February 2015).