A carpet mill can build strength as well as wind. It depends on how it is used. What it can also build is muscular endurance. A critical part of being stronger for longer. The issue with carpet mills from the past is that they were basically a piece of carpet draped over two pieces of pipe. It took an incredible amount of work for the dog to make it move. Couple this with someone who did not know what they were doing and they ended up with a muscled up freak. It takes more oxygen-more blood for bigger muscles so the dog could not 'breathe'. So the carpet mill was dubbed for strength only. Fast forward in time. The carpet mills get end rollers vs. stationary pipe. The sliding surface is some sort of plastic/polymer vs. sanded plywood. The carpet is a lighter yet stronger blend vs. the 1970's shag carpet with jute backing. If I had to choose between the three mills mentioned I would choose the carpet mill every time. EWO