I have 2 layers of OSB board over a paving slab floor,don`t have a problem with cold feet or fatigued legs/feet,at work we had ant-fatigue mats,but in a dental lab they are a pain as they get full of dust and crap to quickly,I like Pauls idea,I used to work with a chap who bought those make yourself moccosins and he cut tyre treads to the shape of them for long wearing soles.