Is it? The makers of FitFlop -- the shoe sold at 4,500 stores around the world -- say the sandal was designed to be a workout while you walk, with "side effects" of comfort and relief from chronic lower back pain.
The premise of the FitFlop's rubber sole with different densities (also known as the micro-wobble board) is that it helps tone because it creates instability during walking, forcing leg muscles to work harder to maintain posture and balance. Skechers and Dr. Scholl's make their own versions.
Dr. Phil Graham-Smith, head of the Directorate of Sport at the University of Salford, did an independent study on the shoe. He said data has indicated that calf and thigh muscles were activated for longer during walking with these shoes, and that the speed of walking was slightly faster.
He's still studying the effects.
"I think the comfort element of it is that you probably feel more motivated to do more exercise as well," he said.
The idea was to mimic the natural roll over of the foot, said Dr. David Cook, senior lecturer of biomechanics at London South Bank University, who along with a doctoral student created the FitFlop. Cook also said toning depends on a person's diet, exercise and duration of wearing the shoe.
I wore the FitFlops intermittently for about two weeks and I did feel the familiar burn of exercise in my knees and back leg muscles. I scanned myself in the mirror daily to see if there was any minute difference and I have to say I felt better, even if I couldn't see a difference.
My pair was red and white, but there are other styles with sequins, suede and bright colors with transparent soles. (Women's sandals range from about $50 to $60, while men's go for about $60.) When I got caught in a torrential South Florida summer rainstorm one weekend, the red dye ran all over my toes making me look like I had cut myself.
A Miami-based orthopedic surgeon and a podiatrist who were asked to examine the shoe both said that wearing an uneven shoe could actually create more problems for people with foot conditions and that sandals are not the safest shoes to wear.
As for an extra workout in a walk? They said it is possible theoretically, but hard to quantify.
"The big question in my mind is to what extent is this enough of a wobble that it actually produces a medical effect, where you're actually toning muscles and building strength," said Marc Umlas, an orthopedic surgeon at Mount Sinai Medical Center in Miami Beach. "The other question is to what extent does it cause damage? We don't know how much this can increase in sprains or strains or other muscular skeletal injuries."
He added that women have been wearing narrow, high heeled shoes that create a wobble for ages.
Podiatrist James Losito of the Barry University Foot & Ankle Institute said walking barefoot isn't necessarily a good thing nowadays.
"Walking barefoot isn't something we would recommend for most people based on the terrains of our civilization," he said.