What are toning shoes and do they work?

Toning shoes, like the Reebok Easy Tone, are designed to make your muscles work harder by giving you a slightly unstable surfarce beneath your feet.  This instability is similar to standing on a BOSU ball or wobble board in the gym.  

The shoes will cause your stabilzer muscles to work a bit harder in your daily activities but it is very unlikely they will significantly increase the muscle tone in your legs.  They may, however, inspire you do get up and walk more and that's never a bad thing. 

It is important to note that you should not run, or jog in these shoes and lifting weights in them would not be not be advisable either. 

The principle behind these is that the design of the shoe’s sole keeps you off balance; and because you’re always working to keep your balance, you work harder, burn more calories, use your muscles more and therefore get a better workout and a more toned body. There is conflicting evidence as to their effectiveness. The manufacturers have commission studies concluding they work. However the American Council on Exercise conducted a study of its own that tested all the major brands of toning shoes against regular athletic shoes.

Their study found no significant difference between the Toning shoes and regular athletic shoes. Here’s a link to the study. http://www.acefitness.org/getfit/studies/toningshoes072010.pdf

As a trainer I have seen countless people that I do evaluations with wear these shoes. Very politely I will ask why they are wearing the shoes?

The answer I receive is generally "I don't know." Ken's answer about helping to improve stability and potentially balance (which can improve joint stabilization) can be beneficial. However the shoes are generally marketed as a shaping shoe or something that most consumers feel that will help them "tone-up" or lose weight. The shoes are no different than any other marketing gimmick that is out there.

No if people understand that they help with stabilization and balance and are using it simply for that reason, know that they should not wear during running and working out and are seeking professional coaching for their workouts, nutrition and lifestyle, then and only then do I think the shoes are beneficial.

I am much more in support of people going to a show store that has people on hand that will look at your feet, arches, walking style and body type and suggest a proper shoe to match what fits your needs.

I am a big fat of Brooks Running shoes (even for working out) and they have a shoe advisor online that can help you pick the right shoe for your foot.