Walking on air

Now that I am back to walking with my crutches in Physio, I have noticed for a while now that when I walk with them in the gym I don't seem to be putting any weight through them. It's like I am walking with nothing, unaided if you like. Although when I walk on the carpet it automatically feels as if I am putting weight through them have progressed back to my crutches. It is an odd feeling and something I have never really understood when this happens. One theory I do have is that carpet as a texture too it and therefore the walking movement who knows maybe someone reading this might have some thoughts