Biomechanics Of Running Barefoot

By Jyoti KheraFebruary 16, 2021No Comments

Even though humans have been walking and running barefoot for millions of years, there has been a recent interest among runners to run barefoot. Different opinions and innumerable research studies have provided conflicting evidence.

In the 1960 Olympics, Abebe Bikila, an Ethiopian runner, won the marathon gold with a time of 2:15:6 while running barefoot. Zola Budd is another barefoot runner who won recognition by setting a world record at the 5,000m race in 1985, finishing at 15:01:83. No major world records have been set while running barefoot over the last quarter century. All current track and field and other running event records have been set with shoes on. However, running barefoot has been gaining a lot of popularity as a way to reduce running-related injuries.

There has been a set of people who have been proposing barefoot running as the best form of running. But is it better? Doesn’t it hurt? What are the advantages or disadvantages of running barefoot? How should someone transition from shod running to barefoot? These questions and many more arise in the minds of athletes, coaches, trainers, physical therapists, and physicians.

In this article, I will explain the biomechanical changes that happen when running barefoot, along with a safe approach to transition from one form of running to another. But to understand that we must first be aware of the impact of running shoes on the biomechanics of running. Please look at my previous article explaining the impact of running shoes on the biomechanics of running and their effect on the risk of running-related injuries.

Barefoot running is basically to run barefoot or in a device that provides no support, heel counter and has no shock absorption properties which leads to more natural running pattern. Barefoot shoes are ultra-lightweight, ultra-flexible from heel to toe, with barely-there barefoot experience. Along with the barefoot shoes, there are options which provide little bit of shock absorption with little or no support throughout the gait cycle. These are called minimalistic and maximalist shoes.

In continuation to my previous article, let me quickly explain the effect of these neutral padded shoes on running biomechanics before diving into the biomechanics of barefoot running.

Impact of Maximalist and Minimalistic Shoes on Running Biomechanics

Maximalist Shoes

A few studies have found that runners may display prolonged eversion (foot turning inside-out) in maximal shoes, which has been associated with injury (of shin/calf and Achilles tendon) both retrospectively and prospectively.

• Achilles tendon (which connects calf to heel), loads at the ankle joint, are found to be lower in the maximal shoe and the patellofemoral forces (at knee and thigh bone Joint) are greater at the knee in maximal shoes compared to the minimal shoe.

Minimalist Shoes

Running in minimalist shoes can cause runners to run with a more plantar-flexed ankle at initial contact and adopt a forefoot footfall (FF) pattern, increase stride rate, reduce stride length, increase ankle plantar-flexor moments (top of foot pointing away from leg), and decrease knee extensor moments (knee stabilization), and slight improvement in the running economy.

Refer to my article for definitions of stride rate/stride pattern/stride length and much more.

The research shows that they decrease patellofemoral joint (knee and thigh bone joint) loading compared to a neutral cushioned shoe, but the calf and Achilles tendon loading may increase while wearing minimal shoes. They may increase the Achilles tendon stiffness and increase the load on the joints, especially ankle.

The minimal shoes often increase the average vertical loading rate and vertical impact peak in rear loading strike pattern which have been associated with a greater risk of sustaining an overuse injury.

Different shoes excel in different roles. So, it’s always better to rotate shoes on running days. For example, a more minimalist shoe might be better for shorter runs, or during cold months or in an unfriendly terrain to help you focus on technique. The traditional running shoes can be used during your long runs when additional cushioning is desired.

Barefoot Running Shoes

There has been an explosion of new barefoot running shoes in the market. The most used minimal shoes recently reported are the Vibram Five Finger, Nike Free, Saucony Kinvara and New Balance Minimus.

When Running Barefoot

Now let’s dive into the biomechanics of running barefoot. Following are the key points to consider when talking about barefoot running.

Muscle activation and proprioceptive feedback

• The activity of various muscles at ankle and leg increases during different phases of barefoot running.
• The intrinsic foot muscles respond more naturally increasing the foot muscle strength.
• It increases the sensory feedback from the contact of feet to the ground as well as increase energy storage in the arch thereby increasing running efficiency. The open barefeet environment challenges the proprioception.
• It stimulates neural function important to balance and agility.

Gait adaptation and the foot strike pattern

Research shows that barefoot runners have a significantly larger step frequency, smaller step length, and less contact time.

• Taking a greater number of steps (larger step frequency) leads to larger plantar flexion of foot. It leads to forefoot strike pattern and reduced load on the hip/knee and ankle joints due to shorter contact time. This reduced load is also because of the less collision forces generated and the ability to absorb shock with FFS pattern.
• The peak leg acceleration is more than twice as fast during barefoot compared to shod running.
• When running barefoot, the foot placement is such that there is a lower peak heel pressure. Therefore, the runners adopt this different touchdown geometry in barefoot running to limit the local pressure underneath the heel. This is another reason which leads to FFS running pattern.

READ ALSO: How To Train For A Marathon? First Step Is To Have A Plan

Shock absorption

Barefoot running produces minimal external protection and shock.

Impact forces: Barefoot runners try to adapt to the running style that reduce the impact force. To reduce or prevent the forces on feet, the body produces more than one impact peak. Wearing shoes causes only one large impact peak, where the forces contact the foot all at once. Running barefoot allows the body to spread out the impact peaks.

The impact peak, or the amount of force put on the foot during first contact, increased from two times the body weight (BW) with shoes to two and a quarter times the body weight while running barefoot. The only difference is that it is spread out.

Barefoot running is also associated with reduced peak ground reaction force (GRF), increased foot and ankle plantarflexion and increased knee flexion at ground contact compared with running in a neutral shoe.

Running related injury risks

Barefoot runners have a much higher incidence of Achilles, calf, metatarsal stress fractures and other forefoot injuries. Much research have been conducted which shows that even though barefoot running reduces the eversion (bottom of the foot facing outwards) or the reduction in the internal rotation of the tibia, still there are not concluding evidence that it reduces the risk of injury.

While potentially related to the forefoot strike pattern, barefoot running is also associated with a reduced stride length, which also has a load-reducing effect. This combination may reduce their injury rate, as high load rates have been associated with numerous running-related injuries. However, a forefoot landing will increase the load to the posterior calf musculature and thereby increase the risk of calf strains and Achilles tendinitis. In addition, a forefoot strike landing can increase the load to the metatarsal heads.

It is unquestionable that the foot is more exposed and thus vulnerable to cuts, bruises, and scratches when barefoot.

Running barefoot clearly exposes the plantar surface to injury. However, the plantar surface is well suited for barefoot movement. When the runner lands on an uneven surface, there is an unexpectedly high load on the plantar surface of the foot. The foot provides the sensory input which encourages an avoidance response, indicated by rapid hip flexion. This in-turn results in a rapid unloading response, which is very similar to one stepping onto small stone.

Transition between shod running to barefoot running

Many professional athletes make this well-balanced decision to transition under the guidance of professional physical therapists, podiatrists, and a fully supportive team of coaches. Recreational runners should be aware of the vulnerabilities of their foot/ankle or knee as there are different forces that act on the small bones of the feet when they run in shoes or barefoot. So, the transition (even the other way around) should be done with caution and gradually.

Here are few things to keep in mind when considering the transition to barefoot running.

• It is imperative that they see a podiatrist/physiotherapist/running coach with sound running knowledge first to develop a program that transitions them slowly to the use of minimal footwear and the adoption of a mild forefoot strike pattern.
• It takes time to develop the foot and lower leg musculature as well as to acclimate to the plantar sensations during barefoot running. A standard transition period is 2–12 months depending on the runner.
• The most common problem associated with transition is soreness in the lower leg and foot. It is important that the runners transition slowly to this new style of running through an injury-free transition.

There is lots of research pending on the long-term effects of running barefoot on foot structure and muscle physiology, and how might these changes be related to injury, effects of running barefoot on long-term bone and joint health and much more. Unless these reach a conclusion, we cannot infer that one is better than the other.

Many factors can contribute to the risk of injury. Strike pattern is just one of those factors, so reduced injury risk cannot just be attributed to barefoot or shod running. Consistency and well-rounded running specific strengthening program are the key to injury-free efficient running.

I very strongly believe that there is no need to change something unless it’s broken. It’s not something to brag about, but I have been running in the same brand/model of running shoes for many years now. If it’s working, then why change?

Photo courtesy: Instagram/@milindrunning