Wednesday, February 5, 2014

Barefoot/Minimalist footwear analysis

In recent years we have seen a rise in the amount of “barefoot training” in the exercise community, particularly in the online community of distance runners. Reports suggest that this year’s Boston Marathon included more barefoot runners than ever before. The popularity of this practice has grown in spite of very little hard evidence to suggest its benefits or the potential risks involved. Due to the lack of scientific analysis on the topic this post will analyze what little research has been done, and look to fill in the gaps with some knowledge of functional human anatomy, knowledge of injury cause and prevention, and logical thinking.

Popularity of barefoot running began its rise upon the release of the book, Born to Run by Christopher McDougall. His book follows the Tarahumara tribe in Africa, known for running extremely long distances without traditional running shoes. The book makes several interesting arguments in favor of ditching your normal running shoe. The tribesmen in question have significantly lower incidences of injury to the ankles, knees and hips. They are extremely aerobically fit and free of the inflammatory diseases that plague our country. Many people took that to mean that they should adopt similar habits.

The original minimalist shoe, the huarache
 It should be noted that the Tarahumara do not run on pavement. Their feet deal with much more forgiving natural surfaces, something we should consider before going for a run without running shoes. They do not sit at desks all day, promoting stiffness and weakness throughout the kinetic chain. They are on their feet throughout the day and it can be assumed that the average tribesman is well ahead of the average sedentary American in any measurement of ankle, hip and shoulder mobility. Upper cross syndrome is far less of a problem in a world with no desks or computers. They are also not exposed to large quantities of over processed food and do not battle an obesity crisis. The impact of barefoot running is not so severe or potentially injurious on the lean 120 pound frame of a Tarahumara tribesman that eats primarily pinole (a more fibrous flour like substance) seeds, and various local produce. This cannot be translated to an individual with a high BMI that fuels him/herself with soft drinks and foods high in processed carbohydrates and trans fats. Even the athletic population cannot really compare itself to the Taramuhara people. The Taramuhara do not resistance train or carry any significant muscle mass. Forgoing shoes during weighted lunges or other unilateral lower body exercises can be detrimental to the big toe or the ankles.

The study upon which a lot of the barefoot community bases their opinions and training habits is “Foot strike patterns and collision forces in habitually barefoot versus shod runners” by Lieberman et al.  The study tells us the following:

The Modern running shoe was developed in the 1970’s by Bill Bowerman and Nike. Its waffle tread was designed to create a lighter base of the shoe while also providing additional grip during cross country races on grass surfaces. It features an elevated rubber heel, which has only become more prominent with time. The elevated heel changes the biomechanics involved in running. Lieberman’s study definitely proves that shod (those wearing shoes) runners are far more likely to heel strike during the landing phase of the running movement (this landing pattern was seen in 75% of shod runners in the study). This heel, or rear foot, strike causes extremely high rates and magnitudes of loading. It is speculated that this loading can be detrimental and has led to the high number of tibia fractures and cases of plantar fasciitis in shod distance runners.

Plantar fasciitis is an overuse injury related to long periods of weight bearing on the plantar fascia. It is experienced by approx. two million Americans each year. In an interview I conducted with Dr. Kevin Kirby DPM, MS he states: “The injury rate of running is more due to training errors (i.e. too much, too fast and too soon), obesity, running on hard surfaces and running in improper shoes and due to the fact that the impact forces in running are 2x-3x body weight versus 1.25x body weight for walking (i.e. running places at least twice the ground reaction force on the foot that walking does), not due to running in shoes per se.” Eliminating such significant heel strike may help to reduce the number of people that suffer from plantar fasciitis. However, it would seem logical to first try a less radical approach of reducing body mass, increasing ankle mobility, or properly progressing your running program.

It seems evident, particularly from Dr. Lieberman’s research that there are some definite drawbacks to having excessive material around the heel when running. The same applies to having excessive material around the ankle and heel during any sort of exercise, or even during daily activities. Habitually shod runners displayed 7-10 degrees less dorsiflexion (ability to take the toes toward the shins or to display a positive shin angle) than barefoot runners. Increasing dorsiflexion ROM can improve functional movement patters. Greater ankle mobility allows for a greater degree of hip flexion during squatting movements without increasing forward lean or rounding of the lumbar spine.

This ROM deficit is not strictly due to time spent exercising with shoes, but an entire lifetime of activities spent in shoes, and can’t be completely cured by going barefoot for a few miles each week. However adding in some barefoot work during some dynamic warmups or slowly incorporating it into a running program may prove to have some beneficial effects on ankle ROM.

Many claims have been made regarding barefoot training to improve proprioception, but there is no research to back it up. This is an area that warrants serious future research. It has been speculated that barefoot training can improve balance, strengthen intrinsic foot muscles and give runners an improved “feel”. It may also help to prevent some amount of heel strike when runners return to their shoes. Being barefoot places a different internal stress pattern on the feet and may help alleviate some overuse injuries by changing the stress involved in ground strike. 

In recent years we have learned a lot of interesting things about the way people run, with and without shoes. However, to this point we have still only observed acute responses to foot strike patterns in a safe environment, ignoring the different surfaces that runners may encounter and the long term, potentially injurious, effects of either forefoot or rearfoot striking on pavement. Given the aforementioned benefits of ankle ROM, and high rate and magnitude of loading in a strong heel strike, barefoot training can serve a purpose as a part of a balanced training program. If you choose to implement barefoot training into your practice or that of your athletes/clients be sure to develop a tolerance at first do so only on a safe surface.

For myself and my clients I do the majority of warmup activities barefoot as well as any deadlifting/hip hinging patterns. If and when I do yoga classes it is obviously done barefoot. I try to be aware of the degree of heel lift in all of my shoes and spend as much time as possible in flat soles to maintain what little ankle ROM I have. During running season I will do my warm-ups on grass with no shoes on and then run in a shoe with a mild heel support. This combination of barefoot training and appropriately shod running has given me a lot of great results so far. I'm always open to hearing new ideas on this front so if you have had a different or a similar experience with barefoot training feel free to drop a comment below. 

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