I had several of the first version of this sandal, which I wore out walking for exercise (on sidewalks and treadmills) and while on vacation. These sandals have less padding under the adjustable straps and shorter velcro connectors. I have found that the velcro edges cut into my heels when walking - which I have solved by putting cotton pads inside the heel straps. Not attractive, but as I only wear these on my treadmill that's not a problem. I'm not currently feeling any toning soreness after working out, but that is probably a combination of having used the MBTs for several years and not walking that quickly...