This summer I was sent to Gold Coast, Australia through my work to attend an academic conference on footwear biomechanics. The science (and pseudoscience) of all types of footwear were presented, but as usual there was an overwhelming number of studies on running shoes. Here I would like to give you an introduction to the development of running shoes over the last decade, and what they have done to help us stay injury-free! Because, amateur or professional, injuries are frustrating and stop us getting out on those trails..!
The injury problem
Runners are an often injured bunch; a relatively recent review of the literature showed we get injured between 20% to 80% per year. Despite the efforts of researchers, we still can’t really pinpoint why it is we get injured. The book Born to run suggested we lost touch with the way we were evolved to run; putting shoes on our feet and running on tarmac. In the scientific world, Lieberman’s article (2010) in the prestigious journal Nature turned the running shoe world upside down with their study, comparing two groups of runners: one group had grown up wearing shoes, the other did not. They found that people who never run with shoes (barefoot runners) land on their forefoot and that this generates less force. Shod runners (like most of us) have the tendency to land heel-first and generate an initial-impact spike in force. It was hypothesised that higher forces increase the likelihood to get injured. The barefoot craze, and subsequently the minimalist footwear rage, was born.
But changing to minimalist footwear and to a forefoot landing did not mean we stopped getting injured. If anything, it shifted the injury to different parts of the body. The running shoe industry responded with the ‘maximalist’ shoe, which is comfortable, cushioned and will lessen the impact when pounding the roads. Next to that, there are still many different shoes on the market, such as ‘motion control’ shoes, ‘zero-drop’ shoes, shoes for overpronators, underpronators, with or without inserts, calcaneal stabilisation, and the list goes on.
Influence of running shoes on injuries
So why is it we have not figured out what shoes will help us stay injury-free? The first problem is we do not know what causes our running injuries. Is it high forces, like Lieberman’s article suggested? Or is it a misalignment in the joints, causing these forces to load the joints off-centre? How would we go about measuring this? And even if we can measure it, do runners run in the same way when they are on a treadmill, connected to wires, observed by a researcher?
Our second problem is that it is difficult to distinguish correlation from causation. For example, we ask a group of marathon runners with and without knee problems what type of shoe they wear. If a significantly larger proportion of marathon runners with knee problems report wearing a very cushioned shoe, it does not mean that the shoe caused their knee pain. It is also possible that the runners (subconsciously) tend to buy cushioned shoes because those shoes felt more comfortable to their sore knees.
To distinguish correlation from causation, it is important to investigate the effect of running shoes on injuries through a better study design. The best way researchers can do this, is through something we call a randomised control trial (RCT). It means you get a group of not-injured runners and randomly assign them a shoe condition. Condition 1 is the ‘new’ shoe that you want to test, and condition 2 is a normal shoe. You send the runners off to let them run for a certain period of time (3-12 months), and find out which shoe-group was more likely to get injured. The number of RCT’s that are done in footwear research is low, because you have to wait a long time for your results and they are expensive. Further, though RCT’s might give you an answer whether or not people got injured, they still won’t explain why they got injured!
Where to go from here?
At the 2017 Footwear Biomechanics Symposium, the question where we should be heading with our research was raised several times. It has been pretty clear from previous studies that people have individualised responses to footwear types – meaning that there is no such thing as the perfect shoe for every runner. In other words, whilst one runner could greatly benefit from swopping to minimalist footwear, for another runner this change can actually induce more injuries.
People have individualised responses to footwear types – meaning that there is no such thing as the perfect shoe for every runner
As researchers, we should now try to tease out what it precisely is that makes a shoe work – or not work – for a person. It is then another challenge to figure out how to communicate this to running shops and the runners who are buying shoes. From the industry round table during the conference we found that this last point is still a problem for the shoe manufacturers.
Join the discussion
- What type of shoe do you wear, and why?
- What do you think universities and companies should be researching?
About the author
Bodil is a current PhD student at the Centre for Sports Engineering Research at Sheffield Hallam University. She is interested in footwear research, everything to do with outdoor sports and specifically loves running ultra distances in the mountains.