A few years ago John Mercer was at a shoe store when his friend pulled a pair of Skechers Shape-ups from the shelf and asked, "Do these work?"
Mercer is the right guy to ask. The biomechanics professor has conducted research on what happens to muscles when people run in different shoes, at different speeds, on different surfaces, and even when they are fatigued. And he's been asked by a number of shoe companies to evaluate their products.
But Mercer didn't have an answer for his friend. The quick conversation piqued his interest enough to launch a new line of study. He found that the shoes don't live up to their advertising promise -- but that doesn't mean you should ditch the pair in your closet.
Together with professors Janet Dufek and Troy Santo, Mercer compared three pairs of shoes: Skechers Shape-ups, which have a bowed, unstable bottom; regular flat-bottom shoes; and flat-bottom shoes with extra weight to equal the Shape-ups.
Mercer wanted to get a better sense of muscle activity and calories used (as an aside, he says "calories burned" isn't accurate) during walking. Santo strapped oxygen masks on the 28 student participants (17 women and 11 men) to determine how much they were breathing while walking.
"If we can measure the air going in and out of the lungs, we can figure out how much oxygen we are using, and therefore how many calories we are using to complete the activity," Mercer says. Sensors on the legs of the subjects measured the electrical impulses in muscles as they contracted, similar to what an EKG measures for the heart.
The results surprised Mercer. There was no difference in oxygen consumption or muscle activity among the three types of shoes. Yet, participants reported that they walked differently in the Shape-ups. The reason, Mercer believes, is that humans are inherently lazy. We naturally find the easiest way to do something. "If we go out and walk across campus, we tend to choose an easy gait pattern. By changing shoes or even the surface we walk on, the brain tells the body to change the gait to keep it easy."
So the study's subjects adjusted their gait until walking in the toning shoes was no more difficult than in normal shoes.
Love Your Pair? Keep Wearing Them
Mercer notes that some people may still benefit from Shape-ups, such as those with foot problems like plantar fasciitis. The rocker bottom can take pressure off some parts of the gait cycle, and similar shoes are used often in rehab.
"Just don't buy a pair of shoes because you think you are going to use a bunch more calories or work muscles differently," he says. "Don't buy a shoe based on color, brand, or advertising claims, because there is no magic to losing weight or making walking more enjoyable. You have to find a shoe that is comfortable."
Walking a mile only uses about 100 calories but it is a low-impact activity so you can do it for a longer period of time. The key to using walking in an exercise program is that you have to want to go out and do it. If your goal is losing weight, Mercer suggests increasing your distance and walking at least 30 minutes a day.
"The bottom line is that if someone is not walking now but they buy Shape-ups or other toning shoes as motivation to walk, then that is great. As Americans, we need to do a little more physical activity," Mercer says. "If you get them and lose some weight, don't credit shoes; it is the fortitude of the person doing the work."