Paul Brice weighs up the evidence for a trainer that would have us walk like warriors
Hail the latest revolution in shoe design. Celebrate the end to the mindless time consuming task of exercising and strengthening the muscles of the foot and ankle. Let Masai Barefoot Technology transform your life.
The Masai Barefoot Technology (MBT) trainer has been around for 10 years, squeezing its way in alongside the vast array of training shoes in this hugely competitive and dynamic sportswear niche. Its makers claim that the shoe:
* activates neglected foot muscles
* improves posture
* tones and shapes the body
* improves performance
* helps with back, hip, leg and foot problems * helps with joint, muscle, ligament and tendon injuries
* reduces stress on the knee and hip joints.
The international media hype around MBTs has even gone so far as to suggest that the shoes can help banish cellulite and promote weight loss – claims not far short of alchemy.
Masai Barefoot Technology is based on a simple concept: that the human foot is designed for barefoot walking on soft natural ground, yet most of us in developed countries spend our lives entrapped in supportive and restrictive footwear and walk on hard, flat surfaces. The shoe design is the brainchild of Karl Muller, a Swiss engineer, who derived his inspiration from the low injury rates of the African continent.
Leaving aside the obvious differences between the functional requirements of the average Masai tribal member and the average office worker/amateur athlete, does this shoe design add up to anything more than a gimmick in terms of injury prevention?
There is no denying the fact that ordinary shoes do little to correct poor gait. Most of us prioritise comfort or fashion in a shoe or trainer over our specific functional or anatomical requirements, with the result that we adopt a passive gait, in which the foot, ankle and leg muscles become under-worked and develop weaknesses.
Strong intrinsic foot musculature is what allows the tissues of the foot and ankle to tolerate the stresses and strains of instability effectively and without damage or injury. It is therefore not unreasonable to suggest that areas of weakness can also be prime sites of potential injury.
There is as yet no solid independent evidence that proves it is possible to strengthen specific musculature by wearing a particular type of shoe.
We can say with some confidence that where an individual has a particular foot type (pronator, supinator) involving excessive movement, the wearing of shoes/trainers that limit or restrict these movements is likely to be beneficial in limiting or reducing the risk of injury. On the other hand, shoe support can simply mask the underlying problem without tackling the weakness that may result in injury.
The MBT was originally designed as a medical shoe. It is a slightly unsightly, bulky shoe, with a substantial thick curved sole, running from anterior to posterior, which forces a pronounced heel to toe walking action. The unstable rocking action is thought to promote and stimulate the natural instability of walking over undulating ground (similar to the daily activities of the Masai tribes) and thereby encourage beneficial muscle strengthening.
To date there appear to have been three main scientific studies on the MBT trainer and its effect on gait characteristics.
The first piece of research came from the Human Performance Laboratory in Calgary, Canada. The research group studied the mechanical effects of the MBT on eight subjects, looking at their kinematic, kinetic and muscular activity patterns, soft tissue vibrations and oxygen consumption during stance and walking. Most of the group’s findings apply to walking only. The MBT was shown to:
*increase rotational ankle movement, notably plantar flexion and foot inversion (particularly in the first half of ground contact)
*decrease ankle joint impulses for the knee joint, which means that the knee has to withstand fewer repetitive rotational stresses (27% reduction)
*increase the user’s oxygen consumption by 2.5%
*increase movement of the ‘centre of pressure’ (COP) during standing, which allows force to be dissipated across a greater area of the foot. High forces going through small cross-sectional areas of the foot are strongly linked to an increase in injury incidence with repetitive foot strikes over prolonged periods.
Based on these findings, the researchers report that the MBT strengthens the intrinsic muscles of the foot and ankle complex, while reducing loading through the ankle joint. But this study had small subject numbers and conducted its analysis at relatively low walking speeds (less than 5km/hr), which limits the usefulness of its findings. We would certainly want to see more research, including a look at the impact of the MBT on a variety of foot types.
The second relevant piece of research was a gait evaluation study by a research group from Sheffield Hallam University, England. The team observed footfalls over a force platform, noting the differences in kinematic and muscular activity between normal trainers and MBT design. They found, in summary:
*Less forward lean: MBT promotes a more upright posture, which may affect the position of the centre of mass at foot strike. The further the distance of the foot when making contact with the ground the greater the braking forces that occur on the body. The authors imply that the MBT reduces braking forces, which does make mechanical sense, as anything that promotes a more upright posture tends to lead to a more efficient system and reduced load through the body
*Higher dorsiflexion ankle angle: the rocker system of the shoe, based on a ridge placed across the midfoot, forces the foot into a greater dorsiflexed position throughout the gait cycle. This would promote a rolling of the foot, which would distribute forces evenly through the feet, allowing the body to absorb force quickly, without injury.
*Reduced ‘transient peaks’ with MBTs: transient forces transmitted through the skeleton as a result of impacts during normal walking and running are a primary factor in the development of many musculoskeletal disorders, such as osteoarthritis, stress fractures and plantar fasciitis (Whittle, 1999)
* Muscular recruitment using MBTs allowed increased activity in gastrocnemius, biceps femoris and gluteus maximus but a decrease in multifidus, perhaps because of the more upright posture and production of greater propulsive forces.
A third research group, from Edinburgh, Scotland, compared the plantar pressures during gait among 22 subjects wearing MBTs and normal trainers. For the MBTs, It found:
*reduced plantar pressure in the heel (probably the result of the MBT design in which there is no cut-away on the heel section)
*reduced peak pressure in the mid foot (21% lower) and heel (11% lower)
*average pressure was greater in the toes and forefoot and less in the mid foot and heel.
*a shift in the pattern of the centre of pressure, allowing force o be dissipated over a greater area of the foot.
People suffering with conditions such as osteoarthritis or other degenerative diseases of the bones or joints may benefit from the reduction offered by MBTs in joint loading and the heel to toe rocker.
It would not, however, be suitable for anyone involved in multi directional sports such as squash, tennis or other team sports. Because the sole design (rocker system) works only in the anterior to posterior direction, the shoe is primarily designed for ‘single plane’ activities such as walking or linear jogging. Moreover, the large and bulky sole unit may not be suitable for multi-directional sports where shoe feel, lightness, durability, etc are important considerations.
We don’t yet have any research into any possible longer term benefits of MBT-type footwear. We would also need research on how the shoe design performs during faster locomotion, when the foot strike may occur further along the foot. While there are manufacturer’s claims for the MBT’s efficacy in relation to jogging, there is no evidence to support them. Athletes using a more pronounced mid foot or even forefoot strike with the ground will find this kind of sole design irrelevant.
The bottom line? As things stand, it would be playing safe to advise your clients never to wear their MBTs in isolation. No single piece of technology, however great the claims are, should substitute for a well structured and balanced conditioning programme that incorporates the essential components of strengthening the intrinsic foot muscula- ture. There remain no short cuts that allow us to omit those boring foot exercises.