Why your cushioned trainers might actually be increasing your knee injury risk

knee injury risk

Thinking of kickstarting a healthier lifestyle through running this year? Planning to ramp up your fitness regime? Or just looking to upgrade your kit? When it comes to running, footwear is often the most important consideration and there are a lot of options out there when it comes to trainers. The most tempting options on the market can be those with highly cushioned soles, as at first glance, the benefits are obvious: more cushioning in the sole means less jarring on the knees, right?

Well, according to a study recently conducted by Finnish researchers, extra-cushioned trainers may be doing more harm than good: not only did the researchers find any evidence that proves bouncier soles prevent injuries, but they can also lead to an increased risk of knee damage over time.

More spring, more sting?

The study, conducted by a research team from the University of Helsinki, took a dozen dedicated runners – all healthy, and all with a professional background – and put them through a 3D running analysis while wearing two different trainers: the Hoka Conquest (which has a 43mm cushion beneath the heel), and the Brooks Ghost 6, (which boasts a 33mm cushion). The study group jogged at both 10km per hour and 14.5km per hour.

According to the results, which were published in Scientific Reports, the difference between running habits in both trainers was literally striking: they revealed that the runners’ feet hit the ground harder when they were wearing the cushioned trainers – particularly at the faster speed of 14.5km per hour, where the load impact in the more cushioned trainer was 12.3 per cent greater than in the less cushioned pair.

It doesn’t get better in the long run

When the video analysis was consulted, the reason why was clear: it demonstrated that the runners bent their knees and ankles less when they wore the cushioned shoes, which caused their bodies to slow down quicker and placed extra stress on their legs. In other words, the feeling of extra cushioning lulled the runners into a false sense of security, caused them to subconsciously unlearn good running technique, and essentially altered the natural spring-like mechanism in their legs which ensures we bend our knees and ankles to create a bouncing movement.

This ‘unlearning’ causes runners to land with a stiffer leg, which ramps up the risk of knee injuries, and can store up a welter of problems for runners of all experience levels. For the professional, it can unravel a technique which has taken years to perfect and hone: for the beginner, it can set you on the path to poor fundamentals right from the off. In all cases, stiffer leg technique ramps up the risk of stress fractures.

While the research team is keen to stress that further studies are needed to confirm and refine their current findings, and that there probably isn’t an across-the-board ruling on cushioned soles, this makes a lot of sense so far. Our advice is to always remember the fundamentals when trying out new footwear, and don’t be afraid to go back to what you know if you feel your new trainers aren’t working out for you. Seeking an assessment from a knee specialist is also important – with almost half of all overuse injuries affect the knee joint, it’s not surprising that there’s even a condition called ‘runner’s knee’.