KTH Research Explains the Impact of Modern Running Shoes
Modern running shoes have fundamentally changed the sport of running. At KTH, researcher Stefan Hallström studies how shoe design affects performance, and the results clearly show that the mechanics of today’s advanced models provide measurable advantages. In collaboration with the Swedish School of Sport and Health Sciences (GIH), methods are being developed that could form the basis for future regulations in international athletics.
“Records and performances in long-distance running have increased dramatically over the past ten years, at a much faster pace than before. Many within the running community have long suspected that this development is not solely due to harder training and improved conditions, but rather something much more tangible, namely the running shoes themselves,” Hallström explains.
Stefan Hallström, Associate Professor of Materials and Structural Mechanics at KTH’s Division of Lightweight Structures, has together with colleagues at GIH developed methods to scientifically measure the mechanical properties of running shoes and their impact on running performance.
The Background to Research on Running Shoe Mechanics
The research began when Tony Arndt at GIH received an inquiry from World Athletics, the international governing body for track and field. The organization wanted to know whether it was possible to develop standardized methods to analyze running shoes and thereby enable future regulations. Hallström describes it as a “chance encounter” that led to an extensive research program. Since then, he and his team have tested more than 100 different shoe models, including both recreational running shoes and spiked shoes used by elite athletes.
“A key milestone for elite runners came in 2015–2016, when the first Advanced Footwear Technology (AFT) shoes reached the market. They are characterized by thicker and more elastic midsoles, carbon fiber plates that provide additional energy return, and constructions that make the shoes stiffer yet more responsive. The result was that professional runners around the world began setting personal bests at a faster rate than ever before,” Hallström explains.
At KTH’s structural laboratory, there is a custom-built piece of equipment that complements the universal testing machine. This setup controls and measures force and position with high precision and, in combination with various specialized test rigs, can be used for a wide range of experiments.
Standardized Tests of Running Shoe Performance
The research group primarily conducts three standardized tests:
1 & 2. Compression at the heel and forefoot
These tests measure the shoe’s energy absorption under vertical loading. Measurements are taken at two points because runners vary in whether they predominantly land on their heels or on the forefoot.
3. Bending stiffness
This measures how stiff the shoe is when bent, similar to the push-off phase of a running stride.
The measured properties have been shown to strongly correlate with running performance in laboratory environments.
“The improvements in performance matched almost perfectly with what we measured in the tests. There is no doubt that the mechanics of the shoes affect performance,” Hallström emphasizes.
There has also been discussion, within the running community, about whether AFT shoes benefit women more than men, since women’s performance curves have increased slightly more over the past decade. However, Research from KTH and GIH shows no evidence to support this. The improvements are essentially identical for both sexes. Hallström instead suggests that a more plausible explanation is that women today have greater opportunities to pursue professional careers and train full-time, which may explain the difference rather than any differential benefit from the shoes themselves.
Ongoing Research Influencing Future Regulations
The original assignment from World Athletics focused on developing fair and reliable testing methods. Hallström argues that highly detailed regulations such as limits on sole thickness or the number of plates allowed in a shoe, make it difficult to keep pace with rapid innovation from footwear manufacturers. Instead, he advocates regulating shoe performance by testing their mechanical properties.
“It doesn’t matter what the shoe contains. If it exceeds the threshold values for energy return or stiffness, then it is not approved. That would make the rules much clearer and easier to measure and apply,” he explains.
Alongside work for World Athletics and GIH, the team is also conducting research funded by the Swedish Research Council. Their most recent article was submitted on the same day this interview was conducted. While the group occasionally tests prototype or record-breaking shoes such as the extremely stiff spiked shoes used by Armand ‘Mondo’ Duplantis. The main focus remains on understanding the mechanics that make modern shoes so effective.
Hallström and his colleagues are at the heart of a development that affects everything from elite athletics to recreational running.
“As technology continues to advance and manufacturers push the limits, this research becomes increasingly important, both for ensuring fair competition and for understanding human movement. Runners may well adapt their technique to better exploit the properties of new shoes, which could potentially increase injury risk. On the other hand, similar developments in footwear could also lower the barrier to running for people who would otherwise struggle, and that is undoubtedly a positive outcome,” Hallström explains.
At KTH, the work continues with running shoes, test rigs, machines, and a growing dataset that provides new insights with every step.
Text and photos: Jelina Khoo