Toning shoes are that sector of the footwear market that have design features that are supposed to make the foot unstable. This instability is claimed to be responsible for the additional tone up that these shoes are supposed to give. The evidence that these toning shoes actually do this is limited and has led to litigation against some of the manufacturers.

Curated Resources:
http://www.podiatry-arena.com/podiatry-forum/tags/index.php?tag=/toning-shoes/ (Podiatry Arena)
http://podiapaedia.org/index.php?title=Toning_shoes (PodoPaedia)
http://www.toningshoestoday.com/ (Toning Shoes Today)
http://www.professorlifeuniverseandeverything.com/exercise-shoes-and-legal-action/246/ (Prof of Life)
http://www.esports-medicine.org/why-the-toning-shoe-marketers-got-busted/225/ (eSport Medicine)
http://www.drthefootwithoutthedoc.com/do-toning-shoes-help/45/ (Dr the Foot)
http://www.therunninginjury.com/my-advice-on-toning-shoes/57/ (Running Injury Advice)
http://www.angrypoddoc.com/toning-shoes-make-me-angry/12/ (Angry Pod Doc)
http://www.craigbpayne.org/category/toning-shoes/ (Toning Shoes Bookmarks)
http://www.snakeoilquackery.com/toning-shoes-as-snake-oil/9/ (Snake Oil)
http://www.soapboxsunday.com/toning-shoes-on-late-night-television/ (SoapBox)
http://www.runresearchjunkie.com/do-toning-shoes-work/ (Running Research)