Should running shoes really be exchanged after 500 kilometres, as some manufacturers recommend? This question is being considered by students at the Institute of Sport Sciences who are investigating how shoe wear affects the biomechanics of running.
Simon Bäcker is jogging on the treadmill at Kiel University’s motion lab. His legs are fitted with various sensors and skin markers which measure muscle activity, among other things. Even his shoes are fitted with pressure-sensitive insoles that transmit data to the computers. 17 special cameras record each step he takes. The student is testing the sensors, which are being used by a team of seven students led by sports and exercise scientist Dr Stefan Kratzenstein to obtain a wealth of measurement data for the study “Schuhverschleiß” (shoe wear). The data is supplied by nine practised free-time sportsmen and sportswomen aged between 20 and 50 years old, of varying height and weight, who will all run 500 kilometres within three months for the project.
“At the start of the study, we equipped the test participants with brand-new shoes and put them on the treadmill to calculate the starting values,” explained Julia Habenicht, who is analysing the data within the framework of her Master's thesis. Every 100 kilometres the sportsmen and sportswomen are examined again, running in the motion lab, to document the effects of the ever heavier shoe wear on the joints and muscle activities. The angle positions of the ankle, knee and hip are measured, the pressure load in the shoe is calculated and the muscle activity evaluated a total of six times.
“The thought is that more muscles have to be activated to keep the leg and foot stable when running in worn shoes,” explained Bachelor's degree student Janne Gleeson. He also suspects that the shoe’s shock absorption on contact with the ground changes over time if the upper material of the worn shoe is softer than it is when new. “On the one hand, we are interested in whether biomechanical changes occur after 500 kilometres and on the other, of course, in how great the differences have to be in order for them to actually be measurable,” explained Kratzenstein.
The tests show that daily running has an impact on the footwear. “After a good 100 kilometres the shoe was well broken in for the majority of the test participants,” explained Sport Sciences student Patrick Nehr. “After 200 kilometres the soles were already visibly worn in places.” Individual evaluations for each runner will show whether this is also visible in the measurement data. At the end, the results for all nine participants will be compared against each other.
“Due to the small number of test participants we are not able to make representative statements on this,” said Kratzenstein. He added: “Of course, gender, weight and the ground under the runner also play a role in shoe wear, as does shoe type.” Nevertheless, he said, the study has produced its first significant findings: “What is clear is that no universal statements can be made about the number of kilometres run, shoe wear and impact on health that apply to all sportsmen and sportswomen. How long the shoe lasts seems to be different for each individual,” said Kratzenstein. This finding may be just as interesting to runners as it is to specialist sportswear businesses.
Autor: Jennifer Ruske
Study results at www.kielmotionlab.com/schuhverschleiss