I warn of the dangers of these types of shoes in The Barefoot Book.
Skechers Shape-Ups are modeled after the MBT shoe. Both shoes possess a rounded sole that purportedly offers a workout just by wearing them. Scientific studies have shown that MBT shoes work muscles differently, but there's no evidence that these shoes ‘tone' your body, especially the buttocks which are undoubtedly the focus of consumers. However, it is obvious (or at least should be obvious) to anyone who knows anything about the biomechanics of human ambulation that these shoes are dangerous. Not only are MBT and Skechers unstable to the point of risking falls, they alter the human gait so dramatically that injuries are bound to happen. Just ask Holly Ward.
How do toning shoes alter the human gait? They convert the natural stepping motion into a rolling motion. Unfortunately, this is not really unique to toning shoes; virtually all shoes make this conversion, but toning shoes take the ‘rolling step' to the extreme.
I hope this lawsuit will educate more people to the hazards of toning shoes. Perhaps this will move us one step closer to having warning labels put on shoes that dramatically alter gait.