We take a closer look at the trend of functional footwear's promises to get you fit while you walk.
Work out this way
It used to be that shoes were something you wore for comfort, protection or fashion, but a new category of so-called "functional footwear" has entered the equation. These products claim to provide a gym on your feet, promising to improve everything from muscle tone and cellulite to posture and fitness. Favoured by celebrities including Paris Hilton, Jemima Khan and Jodie Kidd, shoes such as MBT trainers, FitFlops and the newly launched Reebok EasyTones are billed as a short cut to streamlined limbs and a flat stomach for those who have little time for the gym. But can a pair of shoes really do all of this and more?
According to the manufacturers who have invested millions developing their take on the functional footwear principle, they can. What most of the brands have in common is a degree of instability embedded into the sole of the shoe that encourages either a rolling or rocking action that, in theory, means muscles must work harder to keep the body in balance. It is an idea that was first put to the test by the Swiss engineer Karl Muller in 1990 after he studied the walking stride of the Masai tribe of East Africa, who are believed to have near perfect biomechanical human motion. Previous research had shown that the Masai's stride caused them to have good posture and little joint pain as well as the appealing side effect of no cellulite. Muller used these findings to develop the MBT (Masai Barefoot Technology) trainer, which with its curved sole that rocks the wearer gently forward became the trailblazer of functional footwear.
With more than one million pairs a year sold in 20 countries around the world, MBTs have developed an almost cult-like following and triggered a range of shoes promising similar benefits. Hardly surprising when the manufacturers claim that "every step in MBTs acts like a mini fitness workout" and "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". Joshua Wies, a physiotherapist and consultant to the MBT company, says that "they work a bit like the wobble boards used by physiotherapists to help people rehabilitate from injuries. They engage the core muscles of the body but reduce loading at the hips and knees so they protect vulnerable joints".
Clinical studies conducted at Sheffield Hallam, the University of Calgary and the Edinburgh Royal Infirmary have shown MBTs to be beneficial for people with back pain, bad posture, bunions and osteoarthritis. Sports biomechanists at London's South Bank University who developed the FitFlop claim that their hi-tech flip-flop design will tone the legs as effectively as a gym workout if worn regularly and say they have research to prove it. Likewise, the people at Reebok who spent more than two years developing the EasyTone trainer say that lab tests using specially placed electrodes have shown that the wearer's buttock muscles are forced to work harder.
But critics argue that scientific evidence for most functional shoes is based on small trials that have been almost exclusively self-funded by the companies involved. Indeed, several independent studies have shown little benefit. One published in the journal Medicine & Science in Sports & Exercise reported a negligible difference in the reduction of joint pain among people wearing curved-sole functional shoes or a good walking shoe. Indeed, many of those in the control group reported less pain when walking in their conventional trainers than their hi-tech counterparts.
Some leading physiotherapists go as far as to suggest that shoes that aim to improve posture can have the opposite effect, forcing wearers to walk in an unnatural way and leaving them predisposed to injuries. Nicki de Leon, a consultant physiotherapist at a clinic in London's Harley Street, says she has treated countless patients who have suffered back pain after wearing footwear with an unstable or curved sole. "A lot of people don't realise that they have an unstable pelvis or some hypermobility in their spine and if they wear these kinds of shoes it can cause real problems," de Leon says. "They do alter the mechanics of walking style, but not in a good way because they work the leg, calf and buttock muscles instead of those in the core abdominal region. That can lead to stiffness and rigidity in the back." Further problems occur if you wear them too often. "Your feet and leg muscles almost forget how to walk normally because they have been forced into this rocking action. That can leave you open to pain and strain when you switch back to normal shoes."
Other experts are less critical, believing that functional footwear does have a place in a healthy lifestyle. Sammy Margo, a spokesman for the Chartered Society of Physiotherapy, advises people to strengthen their core muscles before purchasing functional footwear and then to ease into wearing them. "Start by putting them on for five to 10 minutes a day," she says. "This is especially important if you are desk-bound for most of the day as you are likely to have a weak core section. Don't expect to put these shoes on and for them to cure all your problems."
Lorraine Jones, a spokeswoman for the Society of Chiropodists and Podiatrists, doubts that functional footwear has the ability to strengthen muscles or improve posture better than normal trainers, but says that they do have some benefits. "A lot of them are great for people with bunions or pain in their toes as the rocking action means they don't have to push off from the front of their feet, thereby reducing pressure," she says.
Ultimately, the only real way to tell if they work for you is to take them for a test drive. Until recently, I had resisted the lure of functional footwear, dismissing them as little more than a marketing ploy for manufacturers to sell more trainers. But when I finally relented and went for an MBT fitting to see what the fuss was about, I was pleasantly surprised. Standing in them initially took effort - wearing an MBT shoe is so unlike the flat-footed controlled movement humans are used to that they come with an instructional manual - but within minutes I felt that I was walking with better posture. I could feel my shoulder blades pulling back a little, my hips jutting forward so that I felt taller and, incredibly, more graceful. Since then I have tried other brands, all of which seem much more comfortable for daily walking than my regular running shoes, which means I'm inclined to stride farther and faster when wearing them. Perhaps it is all in the mind, but this former functional footwear sceptic is now sold.