Toning shoes are those shoe that are designed to be unstable. This instability is supposed to make the muscles work harder when wearing the shoes, giving a ‘tone-up’. The design features that do this are things like rocker soles and ‘wobble board’ type features. There were many claims made by the manufacturers of these types of shoes that the scientific evidence did not support. The claims ranged form being able to cure cellulite, to correcting postural problems and given the buttocks and extra tone up. As the scientific evidence did not support the claims that the manufacturers made, there have been a number of legal cases that the company’s have had to settle.
Despite all that, they do appear to have some benefits for some people for some types of problems. Would runners benefit from wearing toning shoes? probably not on a run, but for occasional everyday wear, there may be benefits. The toning shoes use the muscles differently, so mixing it up to exercise different muscles probably have significant benefits for runners. It is probably like everything else – everything in moderation and adapt carefully to the load.