True to size, I am walking heel to toe as suggested because of the ball-like balance effect, so I feel a slight slipping up and down at the back of the Shape-Up's heels. Too bad that Skechers and many other shoe companies do not make a size 10 and a 1/2 . I do feel the difference between the real deal-the original MBTs (patented rocker bottom) and the Shape-Ups because about 2 weeks after receiving the Shape-Ups as a gift,I ordered 2 pair of MBTS(they run smaller than the Shape-Ups). After a week of wearing the Shape-Ups,I feel  that my legs (especially the  back of my thighs) are getting a muscular workout. My very arthritic knees seem to feel better, jury still out on my back as I recently had low back  surgery(one of several). I did practice walking for about an hour each day for a week for balance issues and generally getting used to the shoes, I did this with the MBTs as well.. I can def say I am motivated to walk in these shoes, maybe not as fast as most people, but I am comfortable and feel good knowing I am getting a workout since I am not capable of a more strenuous one  at the gym! My neuro surgeon wears MBTs for years, highly recommends them and explained to me, these shoes are supposed to give you an almost chiropractic alignment of your core which aides the spine. I was told by MBT company rep, there is no need for orthotics either as these MBT shoes retrain your muscles, etc. in your arches and feet. A chiropractor who I know told me to add my soft custom orthotics to the Skechers Shape- Ups I just recently purchased, as he didn't feel they have the support for my arches. I didn't add my custom orthotics to my new MBTs, so I will see how that goes.. My husband as several pairs of MBTs and he does not use his custom orthotics, he loves wearing his MBTs as they are and gets the best support from the all-leather  dress shoe style(no more limping from his bad knee).