In the past, many of you have read our articles and opinions on barefoot walking and running (if not see our article here http://homunculusgroup.com/article-of-the-month). As time has gone on you have seen the results of the work we have done for Vibram (www.vibram.com) on their product the Five Fingers (http://www.vibramfivefingers.com/technology/faqs_board.cfm). In our opinion this Vibram device is the closest to true barefoot walking or running. There are now products in the stores such as the Nike Free and the MBT shoe that over the last few years are gaining popularity. Our job, as we see it, is to report the facts, so here they are:
In a recent issue of Outside magazine there appeared an advertisement for the MBT shoes claiming they are the “anti-shoe, anti-boot, anti-sandal etc”. They imply on their training videos, website and advertisements that this shoe improves posture, protects your hips, knees, feet and low back, helps with ligament and tendon injuries and tones your muscles, apparently from just walking in them. We think this must be a pretty amazing shoe if it can do all that just from lacing up a pair! However, if your radar is up and working, you should be asking some hard questions before you spend over $230 for a pair of shoes that challenge you each moment not to roll your ankle in the parking lot outside the very store you bought them in.
Here are some of our major concerns, questions and reasoning for our harsh but sound skepticism.
If you pick up this rather hefty shoe you will notice two things immediately, both of which have concerns. First, the shoe has a rigid last, meaning the shoe does not bend. It has a beveled bottom design called a rocker which is designed to rock on the ground both forward and backward like a rocking chair (the shoe also appears to have a gentle rocker built into the frontal plane as well which can accentuate undesirable coronal plane foot motion, creating lateral instability, but that is a subject for another article).
We think Perry put it best: proper progression of gait over the supporting foot depends on 3 functional rockers. (1)
Heel rocker: the heel is the fulcrum as the foot rolls into plantar flexion. The pretibial muscles eccentrically contract to decelerate the foot drop and pull the tibia forward.
Ankle rocker: the ankle is the fulcrum and the tibia rolls forward due to forward momentum. The soleus eccentrically contracts to decelerate the forward progression of the tibia over the talus. Ankle and forefoot rocker can be compromised by imbalances in strength and length of the gastroc/soleus group and anterior compartment muscles.
Forefoot rocker: tibial progression continues and the gastroc/soleus groups contract to decelerate the rate of forward limb movement. This, along with forward momentum, passive tension in the posterior compartment muscles, active contraction of the posterior compartment and the windlass effect of the plantar fascia results in heel lift.
This shoe takes away from the 3 natural rockers of the foot which means that the foot is not required to do much other than stand on the platform and let the shoe do the work. Taking it to an extreme, this shoe is really no different than the rocker boot (CAM walker) you might wear on your foot after a fracture, foot surgery or if you have a painful great toe due to Hallux rigidus/limitus or turf toe. CAM’s are designed to limit mechanical forces traveling through the foot by making the foot and ankle quiet, protected and unchallenged by external forces (the effects they have on the knee however, are another story). The rocker boots help to reduce heel impact load, and thus induce a more gently rockered mid-foot impact loading. They “soften” pronation, which reduces force into the foot bones and joints and they ease toe off due to the built in front rocker on the boot.
The MBT, at least according to 1 study, lessens heel strike pressure by 11%, but it also diminishes midfoot pressures by 21% and increased forefoot pressures by 76% (2), which is a significant increase. If there is a forefoot deformity, such as a forefoot valgus or varus, or if there are hammertoes or bunions already present, these increased forefoot pressures may actually accentuate pathology since you are in essence limiting pronation, one of the shock absorbing mechanisms of the foot.
As the studies cite (2-5) the MBT shoes are altering muscle forces through the foot. However, an important question remains, “are these good biomechanical changes for the particular foot/foot type, or are they bad” ? We personally do not believe that someone should depend on a shoe to alter muscular forces, We believe the foot should be strengthened to provide the appropriate and necessary biomechanics and forces for optimal foot function and be strong enough to make the necessary foot adaptations to the task and terrain. It is conceivable that the changes the MBT shoes provide could have actual detrimental side effects instead of positive ones; we believe the rigidity of the shoe’s last and its rocker will in time reduce foot function and weaken the foot intrinsics which are critical for joint protection and stability. The best example we can give of long term detrimental effects are the progressive deformities of hammer toes, bunions and “falling arches” all that result from progressive weakening of the foot intrinsics (6-9). This works on the principle of “if you don’t use it, you lose it”.
The second thing you will notice when you pick up an MBT shoe is that the heel “crash zone” (the area that is first impacted at heel strike) which MBT refers to as “the Masai Sensor” consists of an exceptionally spongy EVA foam. This “crash zone sensor” is extensive and reaches all the way into the beginning of the mid-foot impact zone. Being the shoe nerds that we are, we can say with confidence that we rarely see a shoe with such a soft and expansive rear heel crash zone (in our opinion not even the 2006 Nike Cesium’s crash zone can compete with this MBT soft heel zone).
From what we can tell, this aspect of the MBT shoe was designed to cushion, and possibly more so, reduce heel strike weight bearing. However, there are literature sources substantiating the fact that more shoe cushioning does little if anything to lessen impact forces (10-12) and in fact, can reduce desirable propulsive forces. When walking, by avoiding or reducing heel strike thus entering the contact phase with a greater midfoot strike, you are forced to shorten your stride. This shortened stride can be a good thing in many instances. The midfoot strike maintains the body mass over the feet and hence reduces the challenges on the pelvis and core in the sagittal plane (these are some of the postural benefits that the shoe claims but we need to bring it to your attention that you do not need to buy this shoe to reduce your stride length and lessen heel strike ! An entire book by Danny Dreyer, Chi Running and Chi Walking are dedicated to such changes in gait and running and do not necessitate an expensive rigid shoe.).
The Masai tribesman, whom the shoe is apparently named after, apparently reduce or avoid their heel strike during running. Thus they too likely have more shortened strides and step lengths compared to heel strike runners who “stride out”. Since they are known to be such amazing runners a reduced heel strike running style is assumed to have merits, and it does. However, the Masai tribesmen run barefoot because they have to for the most part; this is because running without EVA cushioning under the heel necessitates one to run without heel strike (Go ahead and try to run barefoot out on the street in front of your house, be sure to attempt to heel strike. What you will find is that it is impossible to heel strike on a hard surface if barefoot, not unless you wish to tear the skin off your heel or have a stress fracture in no time flat !). By avoiding heel strike and embracing a midfoot strike when walking and running, the stride lengths are reduced and the body mass is again more over top of the foot impact zone thus improving ambulatory posture and hence improving core and pelvis stability and control challenges.
Running barefoot with the natural midfoot strike that naturally accompanies it allows the impact forces to occur through the entire foot platform and allows the natural pronation at the subtalar joint to do its job of dampening forces. On the contrary, running in shoes, the cushioning of the EVA heel sole affords a pillow effect, enabling one to “stride out” and achieve heel strike. This is an undesirable trait that shoes enable. At heel strike, there is a deceleration moment of your body mass, this means a shear force on the ground which is why your brain will not allow you to barefoot heel strike when running on a hard, rough surface. So the question remains: Is the MBT shoe really promoting true barefoot biomechanics, or is it just using the exceptionally spongy rear crash zone of the shoe to help one reduce heel strike ? We think the latter. Forcing someone to avoid or reduce heel impact/strike naturally forces you to make contact at mid-foot or forefoot (the latter which is bad). For the most part, a midfoot strike is desirable if you have the core stability to withstand this sudden change in gait and posture. So, another question should be obvious now, “Do you really need an expensive shoe to force you to avoid heel strike when you can make that conscious choice on your own with a little know how and motor re-learning ?
Posture is earned, not forced. Putting a cervical collar around your neck does not earn you posture, it borrows that posture from an external device. The MBT shoes does much the same thing in our opinion.
The bottom line is this, if you want to walk or run barefoot, you should mico-progress into a more minimalistic shoe that bends and gives to motion rather than one which restricts or induces/forces any motion. If trained properly (and there is an exercise progression for the feet, which is specific for each individual) many feet can become stronger and more competent and necessitate less of a shoe. In our experience, inhibiting joint motion and muscular functions with a rigid lasted shoe over time leads to bigger muscular incompetences, weaknesses and problems. Foot intrinsic weaknesses have been known to lead to such problems as bunions, hammer and claw toes, neuromas and the like. We fear that the MBT shoe promotes some of these concerns.
On a positive note, a good use for the MBT shoe is for persons suffering from great toe pain from anatomic problems (as opposed to functional), such as Hallux rigidus/limitus (aka. turf toe). The rigid and rockered last of the shoe prevents motion at the joint and thus reduces pain.
These are some problems we see in the MBT shoe, albeit harsh. Why not read our article on “the naked foot” again (http://homunculusgroup.squarespace.com/article-of-the-month), and make your own educated decision. We think you will become a wiser consumer, especially if you ask the hard questions of both the manufacturers and sellers of these and other types of shoes.
1. Perry J. Gait Analysis: Normal and Pathological Function. Thorofare, NJ, Slack 1992
2. Stewart L, Gibson JN, Thomson CE. In-shoe pressure distribution in "unstable" (MBT) shoes and flat-bottomed training shoes: a comparative study. Gait Posture. 2007 Apr;25(4):648-51. Epub 2006 Aug 9.
3. Nigg BM, Emery C, Hiemstra LA. Unstable shoe construction and reduction of pain in osteoarthritis patients. Med Sci Sports Exerc. 2006 Oct;38(10):1701-8.
4. Nigg B, Hintzen S, Ferber R. Effect of an unstable shoe construction on lower extremity gait characteristics. Clin Biomech (Bristol, Avon). 2006 Jan;21(1):82-8. Epub 2005 Oct 4.
5. Romkes J, Rudmann C, Brunner R. Changes in gait and EMG when walking with the Masai Barefoot Technique. Clin Biomech (Bristol, Avon). 2006 Jan;21(1):75-81. Epub 2005 Sep 19.
6. Hallux valgus--an atavism? Ther Umsch. 2004Jul;61(7):407-12.
7. The Podiatry Channel. Claw Toes & Hammertoes: Overview, Causes, Symptoms, Diagnosis, Treatment http://www.podiatrychannel.com/hammertoes/index.shtml
8. Hammertoes: http://www.footphysicians.com/footankleinfo/hammertoes.htm
9. Michaud T. Foot Orthoses and Other Forms of Conservative Foot Care. Thomas Michaud Newton, MA 1993
10 Oleson M, Adler D, Goldsmith P. A comparison of forefoot stiffness in running and running shoe bending stiffness. University of Calgary. Calgary Alberta Canada. Journal of Biomechanics. August 2004.
11. Aguinaldo A., Mahar A. Impact loading in running shoes with cushion column systesms. J. of Applied Biomechanics. 2003, 19
12. Robbins S, Waked E, Saad G. Materials: Do soft soles improve running shoes ? Biomechanics, April 1998.
