i got a pair yesterday and took them out for a short jog (1 mile or so). so far it's not bad, i can tell that it's different because the bottom of my feet and my calves feel like they had had a mild workout when normally on a short jog like that i don't really feel anything. so far so good... gonna break myself slowly into them. maybe run a mile at a time 2-3 times a week and kind of progress from there.