They look like standard issue NHS orthopaedic footwear, unattractive in the extreme, yet celebrities such as Jemima Khan, Sadie Frost and Jodie Kidd can barely kick off their Jimmy Choos fast enough to put on a pair of MBT trainers. Even Cherie Blair has a pair - and who can blame her when it is claimed that these bizarre-looking shoes can burn fat, abolish cellulite and reduce back pain? So popular have they become that more than a million pairs were sold last year in more than 20 countries; there are 133 stockists in the UK alone, a figure rising by the month. Such statistics are all the more impressive considering the company does not advertise - its cultish status in the fashion world is entirely down to word of mouth and celebrity approval.
What makes these shoes extra-special, says the manufacturer, is their patented physiological design which, it boldly claims, makes them "the first footwear that has a positive effect on the entire body". The shoes, which cost £129 in Britain, were developed by Swiss engineer Karl Muller in 1990 and have a curved sole that promotes some instability and encourages a rolling front-to-back action. This supposedly mimics the walking stride of the Masai tribe of east Africa (MBT stands for Masai Barefoot Technology). Muller believes the tribe to be as close as it gets to biomechanical perfection in humans. In theory, the Masai's stride naturally leads to improved posture and relief from joint pain with the rather pleasing side effect that the Masai have no cellulite. A stride in an MBT shoe is so unlike the flat-footed controlled movement we are used to that they comewith an instruction manual and are sold along with a short training session on how to walk in them.
"MBTs work as a sensory-motor device - similar to a wobble board but with the added benefit that you can comfortably wear them on your feet," says Joshua Wies, a chartered physiotherapist and director of the MBT Academy - set up by MBT to train its suppliers. "This means that they retrain posture and correct movement patterns when standing and walking by stimulating the core muscles of the body. The result is a high volume of low-intensity exercise, and because of the increased muscle activity stimulated by the shoes there is a reduction of joint loading at the hips and knees. At the same time the slightly unstable design of the sole improves pressure distribution in the feet."
Wies points to clinical studies conducted at Sheffield Hallam University, the University of Calgary and the Edinburgh Royal Infirmary that have unearthed some positive effects of MBTs. "People with back pain will certainly benefit from wearing MBTs and they can help problems as diverse as bunions and osteoarthritis. They improve the way you walk and the way you stand."
MBT also claims that "every step we take in them acts like a mini fitness workout", and, as the body works harder to stay balanced, so "the whole body has to work harder from the inside out, stimulating the deep core muscles and toning and strengthening the back, legs and tummy." As a consequence, bumpy cellulite is said to be ironed out while more calories are burned.
But can a shoe really do all that? Certainly, a growing number of cynics doubt the publicity claims. Clinical trials attempting to provide scientific evidence for them have been small and almost exclusively funded by MBT itself. Results of the most recent, and one of the few to be published (in the Medicine and Science in Sports and Exercise journal last year), seemed to be inconclusive, with researchers at Calgary finding there was negligible difference in the reduction of pain among osteoarthritis patients wearing MBTs or a good walking shoe. Indeed, those in the control group reported less pain when walking in their conventional trainers than their MBT-wearing counterparts.
Nicki de Leon, a consultant physiotherapist at the sports and spinal clinic in Harley Street, believes that, for most wearers, MBTs can do more harm than good. "This footwear fundamentally alters the way someone walks, shifting their normal biomechanics so that instead of someone striking their heel to the floor and transferring the weight forward, they are effectively being rocked forward by their shoe." While not disputing that MBTs work some muscles harder, she argues that it is the wrong muscles that are tested. "What happens when you wear them is that the superficial muscles - such as the hamstrings, calfs and gluteal muscles in the legs and buttocks - are worked rather than the deep muscles that support the spine. When any superficial muscle is overworked, it becomes stiff and rigid, and that is precisely what I have seen happening in people wearing MBTs. I am not a fan of them at all."
Noel Kingsley, a leading practitioner of the Alexander Technique in London, agrees that the shoes are overrated. "They encourage a shorter stride than most of us are accustomed to. My concern is that this type of footwear lifts you quite high off the ground and requires you to walk in a special way. Once you get used to them, you feel quite odd without them. So what happens when you take them off?"
It is a question that also concerns de Leon. "A lot of people use them to walk distances, such as to work, but when you take them off your muscles forget what they are supposed to do. When you wear them, they change your alignment, but you don't know what's happening to your posture when you take them off and it's often not good."
In the long term, she says, the rigidity and stiffness of the muscles overworked by MBT shoes can cause pain and vulnerability to other injuries. "They are particularly risky for people with an existing unstable pelvis - quite a common problem - as they compound the instability. I really hope nobody runs in them as the outcome in terms of injuries could be dire." While MBT doesn't actively encourage running in its shoes, it doesn't discourage it either.
Others are less opposed to the concept that a rocking sole might somehow be beneficial. Sammy Margo of the Chartered Society of Physiotherapists says that MBTs can be helpful for some people. Indeed, she has been wearing a pair for three years. "They suit me perfectly and can possibly help other people with stiff backs who do jobs that involve a lot of standing," she says. "However, they don't work for everyone. For people who spend a lot of time at a desk, have hypermobility in their spine and weak core stability, MBTs could make their postural problems much worse."
Wies concedes that MBTs require a particular walking technique that can take some longer to master than others. "It's important to lean into them. And you need to start by wearing them for just an hour or two a day as they can make your muscles ache and cause niggles and twinges."
Alex Hazell, 28, from London started wearing MBTs four years ago. "At first I thought they were great, but then my physiotherapist pointed out that I was getting shoulder problems as the shoe was throwing me forward posturally. In the end I ditched them for a properly fitted training shoe."
Margo stresses that anyone intent on wearing MBTs "should definitely be doing a Pilates class or working on their core stability. Ideally you should get them only on the recommendation of a physiotherapist and should be trained to use them properly. They are not a cure-all for modern life".
