Analysis: a technique like cushioned running may be one way to prevent injuries by reducing loading impact on the body while exercising
Running is one of our favourite forms of physical activity, providing significant physical and mental health benefits. Unfortunately, it can also result in significant injury, with over 60% of recreational runners becoming injured every year.
While many factors contribute to running injuries, all are ultimately caused by loading forces that are too high relative to tissue strength. This is the same for all materials, whether its rope, your favourite cookie or your tissues. To understand why we become injured, we need to understand why loads are so large and how to reduce them.
When running, high loads are applied to your body each time your feet strike the ground. These are two to four times body-weight across the body as a whole, but up to 12 times body-weight across the ankle and knee joints. This load is applied about 1,500 times per mile ran (940 per kilometre).
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From RTÉ Radio 1's Ray D'Arcy Show, Sonia O'Sullivan talks about the Runuary challenge to get people running in January
These loads are cushioned as they travel towards your head. To understand what it could be like if you did not run with an appropriate technique, jump just a few inches off the ground whilst staring at a distinct object ahead of you (but only if you are not injured and promise not to sue me). Land on your heels with completely straight legs. What did you feel? Sharp pain in your legs and back. You also see the object vibrate up-and-down as your eyes actually oscillate in your head from the loading shockwave.
Why hasn't evolution protected us more?
Evolution has faced an 'energy efficiency’ and ‘injury prevention’ dilemma. Historically, food was scarce and running to both kill our prey (persistent hunting) and escape becoming prey required a lot of energy, necessitating very efficient movements. However, we need to avoid serious injuries that would prevent us from hunting or escaping, improving our chance of survival to pass on our genes (natural selection). The evolutionary scales tipped in favour of energy efficiency, as evident from our running prowess, but high number of injuries.
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From BBC Earth, David Attenborough on how the San people of the Kalahari desert engage in the persistence hunt, an intense and gruelling eight hour chase.
Running uses a muscle contraction pattern called the stretch-shortening-cycle, whereby muscles are first forcibly stretched (eccentric contraction) when your foot strikes the ground, then immediately shortened (concentric contraction), which propels you powerfully forward.
Like a pogo-stick, you store energy when landing and re-use it when rebounding. This not only results in faster running, but is energy efficient as it requires up to 40% less energy than a concentric contraction alone. The problem is that the stretch-shortening-cycle's effectiveness improves with higher eccentric loading which is made possible by striking the ground hard when we run - all of which is bad news from an injury perspective.
How can we reduce injuries?
This is where observing elephants can help. Due to their huge mass, they have had to find a somewhat unique evolutionary solution to reduce loading (Force or load = mass x acceleration). They use a more cushioned run than us, by keeping their hips and feet closer to the ground and bending their legs more. We call this 'cushioned-running' or ‘Groucho-running’ after the silly crouched movement of Groucho Marx.
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While I do not recommend the more excessive knee flexion of Groucho Marx, it is relatively easy to run keeping your hips and feet low and flexing the knees slightly more than normal. We are currently developing an app to help learn this technique and our research has shown this results in much lower loading on the body.
Reducing loading whilst running clearly can reduce running injuries. Researchers taught 166 runners over 8 sessions to use 'cushioned' running, using a force-plate embedded in a treadmill to display the force of the runners striking the ground. Over a one-year follow-up, the ‘cushioned’ running group had a 62% reduction in the risk of injury compared to normal runners.
Will cushioned running cause other injuries?
This is an important question, as some changes in running technique result in a shift in loading from one body part to another. For example, runners trying to first land on their forefoot rather than their heel (e.g. barefoot or minimalistic-shoe running) reduces knee loading, but increases forefoot and calf muscle loading, increasing injury rates in these regions.
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Cushioned running vs normal running
However, ‘cushioned’ running is not about shifting the load, but reducing it. Remember, the greater the height an object drops, the greater the velocity it strikes the ground, and the greater the loading. By keeping your hips and feet low while running, your body falls less and strikes the ground with less force.
Will cushioned running reduce performance?
We found that people will naturally run slightly slower (5%) using a cushioned action when running at a self-selected pace, but they can still run at their normal speed if they focus on doing so. Also, the amount of energy expenditure is similar for modest ‘cushioned’ running compared to normal running. If runners choose to flex their knees even further (to reduce loading more), energy expenditure and fatigue will increase. While this would not be good in a race, it would result in you burning more calories and working your heart harder.
So what now?
Most importantly of all, get out there and run to avail of the huge potential health benefits. Don’t let a decision about your running technique act as a barrier. However, if you suffer repeated injuries or have ongoing joint pain (such as osteoarthritis), see if adopting a cushioned running technique can allow you to start running again or to stay injury-free for longer.
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
