I bought these because they looked cool, but as a bonus they are insanely comfortable. They slip on and off, but between the strong elastic where laces would normally be, and the higher "tongue" and back, they feel very secure. I have not (yet) tried to work out in them but am pretty confident they'd stay on just fine. They also provide a lot of support for my heel - it's cushiony without feeling mushy. And again, they look really cool - I get a lot of compliments.