From shoe to foot: Barefoot running

About 10 years ago the running shoe market turned euphoric: Natural Running was the new trend,  at the same time it was the counterdraft of the previous running shoe concepts. But soon it showed that many runners were overwhelmed with the new shoes. But does this contradict the concept of the shoes? Martin Daumer, a convinced “minimalistic” runner, dealt with the topic on a scientific level.

For more than 20 years the sports shoe industry has gone into cushioning and pronation with constantly new technologies and shoe constructions. The aim was to reduce the injury rate through improved stability and control by the shoe and better cushioning. But it increasingly became apparent at the end of the last decade that there is no scientific proof for that. Very elaborated sole designs with strong heel lifts were even under suspicion to harm the foot instead of protecting it.

The first successfully introduced counterdraft to this concept was Nike Free, launched in 2004, that allowed the foot full range of motion, but that also demanded more from the muscles. The success brought the other producers to the scene, so that soon it could be considered a trend. Running was supposed to be more natural, better, injury-free with these shoes, that all had a flat, flexible sole. And shoes went on sale that are little more than a slipcover for the foot. The initial elation soon slowed down with the first reports on overloading damages caused by the shoes.

Many athletes returned to the conventional running shoe concepts or more supporting shoes requiring less muscular stabilization. Since that time barefoot running shoes have had a hard time in the trade, because no shoe retailer knows if his customer is ready for a possibly longer transition phase or if he runs directly into overloading. Martin Daumer, physicist, mathematician and professor for “Computational Medicine” at the TU München, is a dedicated long-distance and mountain runner and designs barefoot running shoes himself. He asked runners in an international study that successfully managed the transition (see box on page 22). He explains in an interview why he believes that barefoot running shoes are sold short in the market:

Mister Daumer, in your study some runners told you that by switching to barefoot running they got rid of overloading problems that they suffered from with normal shoes. Should all runners change over to barefoot running in order to avoid problems?

If somebody does not have any problems, there is no reason for him to change his running habits. Because if he changes the shoe, possibly also the running style changes and thus the load and the risk of overloading. This problem exists in every kind of sports if you change something. In case of cross-country skiing there used to be only the classic style, until skating came up that was a lot faster.

With the transition there were however many injuries, so that skating in the beginning was considered a very risky technology. But the muscles and the tendons simply were not trained sufficiently for this technology. Today skating has been established as an independent technology.

That is no different with barefoot running. People are quick to underestimate that here you have a completely different motion and load process as with running with shoes. The body can adapt to this, but you have to allow time for it. “Too much, too fast”, was the explanation quoted the most by runners in our survey why there were injuries during the transition. The runners asked too much of themselves during the transition.

Are there any clues when it makes sense to change shoes and/or the running style?

That is hard to say, also because there has been a big change in research in the last years. One of the most renowned sports shoe researchers, Benno Nigg, admitted some years ago that what used to be considered as trigger of injuries – mainly overpronation and lacking cushioning – could not bear scientific testing. Today there are new theories, such as the preferred motion path of the joints or comfort as indicator for the selection of the correct shoe. Also this has to be still scientifically established and proven in practice.

Scientifically you cannot say clearly if running shoes so far have led to a reduction of injuries at all. A classical problem when running is a knee problem. It has been cited frequently in our survey and there are some runners who overcame this problem with the change of normal shoes to barefoot running shoes. But these are statements of individual runners and no hard scientific findings.

Could we predict typical injuries in a running analysis and then recommend a change?

Unfortunately there are only few sophisticated studies in this area. Most studies are in addition based on lab tests. These can be transferred only in a very limited way to the running practice. The problems do not occur in the lab, but in the many, many hours when people run outside. That is why I feel that clinical studies in the future will use mobile sensors, so-called wearables, to measure the everyday life of the runners.

This way it is probably easier to detect if and how running technology and footwear impact the development of injuries, especially if the runner is tired. Over the course of an entire race, such as a marathon, you can see how the running style changes that often is very different from the one you can see in the running lab. But it is not clear yet how I can detect data during a race or in everyday life of runners that indeed provide information on loads.

If a runner changes to a barefoot running shoe or a minimal shoe, what should he be prepared for?

For the pure barefoot run you have to consider the skin first. The skin of the footsole is not robust any more and can be easily injured. On the other hand you will not get any blisters from shoes. Muscularly mainly the metatarsus and the calf muscles with the Achilles tendon are stressed. They are exposed to clearly higher forces than in case of the heel run. The calf muscles can suffer from a classic muscle ache, but also from inflammations or ruptures of muscle fibres.

Overloading of Achilles tendons can lead to chronic inflammations or to a rupture. Also the M. tibialis posterior that sets the foot upright, has to work more if the foot is not supported by the shoe any more. For that there are no studies, as far as I know, whereas the stronger stress of the calf muscles and the Achilles tendon is well proven in literature.

What kind of stress is dangerous for the runner?

That always depends on how well the runner is trained. But sometimes it does not take much. We once tested three runners that had a similar standard of performance, one, that always runs in normal sports shoes, one in the transition phase towards barefoot running and an experienced barefoot runner. All three ran without any problems a distance of about 400 meters in shoes, and two weeks later the same distance in minimal shoes.

The runner in the transition phase suffered from unexpectedly strong muscle ache in the following days, and the runner that has not run in minimal shoes before, even had to stop his training for several months because he overstrained his muscles and mainly the Achilles tendon. That is why you should not run more than 200 meters with the unfamiliar shoes in the beginning and only very slowly increase the distance. We cannot caution runners enough about an overload. If only once I was too fast or did too much, a long-term injury can follow.

If you can do too much too fast, then there are no typical warning signals for an overload, I imagine?

Every runner knows that after a certain time of running the experience of pain is reduced and you can bear more pain than usually. During running you will not necessarily notice that you overload yourself. If you are a barefoot runner and you really run long distances, there are phases when your calf muscles get tired.

After the forefoot touch the heel crashes to the ground without brakes, because the calf muscles cannot dampen the impact. If then the experience of pain is reduced, it can lead even to a broken heel bone. There are some cases described in the literature.

Does it help to wear the shoes in everyday life first during the transition phase, also if the load when running is actually different?

I do not know of any studies that show that this makes sense. But it certainly is not unreasonable. But you always have to be aware that the stress later on when running is much higher. If you want to get used to it, you have to run with the shoes, but in the beginning only very short distances.

You should also not make the mistake of running on soft underground such as for example sand. This is a completely different type of running and strains the muscles even more and first of all totally differently. A more solid surface makes more sense here, either forest floor, but also asphalt.

How do you run correctly barefoot or with minimal shoes?

I would ask first how a running style typically changes if runners change their shoes? If someone runs barefoot or with minimal shoes, very often the stride frequency increases and the step length gets shorter, at the same speed. The foot touches down closer to the body’s center of gravity and the so-called overstriding is reduced.

Overstriding means that the foot touches down with the heel far before the body’s center of gravity and first a blow back occurs that has to be overcome. Many runners run “at low revs” too much, which means with a stride frequency that is too low for the given speed and they compensate that with a bigger step length.

The higher stride frequency actually has the effect that I put my foot more beneath than before my body and I thus run more gently?

Yes, and this can be easily implemented, also with shoes. If I increase my stride frequency, almost automatically the running style and the foot strike changes. And some experts say that this is the way towards a healthier running style. A guidance level is about 180 steps per minute, of course depending on the training state and in case of quite some speed, from about 11-12 km/h. This is a parameter that can easily determined and that is easy to understand for runners.

If someone was a heel runner with shoes and runs then barefoot or with minimal shoes, how does that change the running style?

Usually he will not be a heel runner any longer. But this is not necessarily so. If you do not only measure in the lab but also in a real run, there is more variability in the running styles than what you would think. If for example a barefoot runner runs a cross run and runs straight ahead on soft forest floor, he will change to a metatarsal or heel run once he is tired. This way the calf muscles can get some rest.

And if the underground gets harder again, he changes back to the forefoot. You always adjust to the underground when running. This is why you have to go outside with your analyses. This cannot be seen in the stride lab. How much influence does my footwear have on my running style?Of course the footwear impacts the running style. Daniel Liebermann, who influenced the discussion on barefoot running decisively with his works, says:”How people run might be more important than what is on their feet. But what is on your feet can influence the way you run.”

If you wear heavy shoes with a thick cushioning beneath the heel, you will be more frequently a heel runner that takes big steps than a runner with a shoe with a thin, flexible sole. But if you concentrate, you can also implement a clean forefoot run with a heavy shoe.

Does that mean that once you have internalized a motion pattern you can also defend it against the shoe?

You have to learn it before and you have to implement it consciously. There are some shoes however where this does not work mechanically, because the heel lift is too big and you cannot stretch the forefoot enough in order to touch the floor before the heel. You write in your study that it can take a very long time until the neuromuscular system is adapted to the loads of the forefoot run? What does that mean in terms of weeks, months, kilometers?

Unfortunately there are no convincing long-term studies for that. It is more a conclusion by analogy, that you can deduct how long it takes from the experience of runners, from books on the topic or from surveys among runners. One thing however is sure: I will not turn into a barefoot runner by simply taking off my shoes. Due to my own experience and to the experience in the literature, I estimate that it takes at least two years until you can say I am an experienced barefoot runner.

It needs time and many run kilometers, until the many trivia and optimizations in the neuromuscular control that are important for a “good”, so to speak adjusted to the individual marginal conditions of the runner, barefoot running style becomes your second nature. This is probably the reason why some runners are said to run elegantly and beautifully and others do not.