Rocker soles boost posture, but not great for shaping up

Better-toned thighs! Firmer buttocks! Such are the sales pitches by manufacturers of rocker-sole shoes. But shoes alone do not a dream figure make.

Rocker-sole shoes have been around for a while. In 1996, the Swiss company Masai Marketing & Trading launched Masai Barefoot Technology (MBT), footwear it said simulated walking on natural, uneven ground - for example, sand.

Newer generation rocker shoes also claim to mimic the "naturally" unstable human gait.

"You could call rocker-sole shoes instability shoes," remarks Ewald Hennig, a professor at the University of Duisburg-Essen's Institute of Biomechanics. Having to compensate for the instability is beneficial, he says.

"It results in a more varied gait pattern and lets us learn new motor programs," Hennig explains. "Muscles are used more, and in a more varied way, and there is less strain on the knees and back."

The shoes, in short, are a boon to modern man, who treads on unyielding pavement day in and day out.

"We almost always walk on hard, flat surfaces with the same gait nowadays, which is actually unnatural," Hennig says.

The instability of rocker shoes comes from rounded soles in the case of MBT. With EasyTone, the latest line of women's shoes by the United States-based sportswear company Reebok, it is created by air moving between pods under the heel and forefoot. Both types take some getting used to.

"You shouldn't wear the shoes longer than 20 minutes a day at first," advises Nils Stenbock-Fermor, an orthopaedic surgeon in the German city of Aachen.

To correct for the shoes' instability "you've got to change your usual gait, which engages a different group of muscles," explains Thomas Obens, a physician at the Private Institute for Applied Biomechanics in Germany.

Obens says it was scientifically demonstrable that different muscles were used, but he expressed doubt that the shoes' professed effects could be achieved. And the unaccustomed way of walking can overstrain some wearers' legs.

"At any rate, you don't get firmer buttocks and better-toned thighs simply by wearing such shoes," declares Hennig, whose tests have shown that the group of muscles used is most different when the wearer is standing and not, as might be expected, walking.

"Standing isn't exactly an activity that burns a lot of calories, though," he adds, which means that hoping to lose weight with the shoes is illusory. "Compared with normal shoes, you'd have to stand in rocker-sole shoes two hours every day for a year to lose 1 kg," he says.

To really develop muscles, Hennig says, you have to work them to their limit with strength training. Wearing rocker shoes does, however, change posture, he says, and gives "the same optical effect as high-heeled shoes."

"On the whole, rocker shoes get a positive evaluation," Hennig concludes, noting that instability while walking would benefit almost everyone and could help prevent orthopedic problems. But he said the shoes were inadvisable for people who already have difficulty walking.

"Elderly people, too, lack the coordination needed for unstable walking," Obens points out.

Everyone else is suited for rocker shoes - but not to jog in. "Rocker-sole shoes are like a piece of training equipment. They're suitable for daily walking and Nordic walking," Obens says.

For running, there are Swiss-engineered, spring-soled Kangoo Jumps. "With them, body weight is transformed into kinetic energy, which causes the runner to rebound," explains Stenbock-Fermor, who said the fun shoes were a good thing for well-coordinated, athletic people.

Kangoo Jumps are not cheap, costing upwards of 200 euros ($257), similar to MBT shoes. Prices of EasyTone shoes, on the other hand, start at 90 euros in sporting goods stores.

People who want airy shoes with an instability effect can spend 40 euros and up for FitFlops, made by a British company.

German Press Agency

(China Daily 10/02/2010 page8)