Yes indeed, its interesting the different quantities I've noticed - like up to 17,000 my body really ramps up, I could do that every day, and often do, but I did 30,000 the other day I was tired the next day. Though when I started 5,000 was a major achievement. I'd love to see wider studies on this, like do muscles change? and how etc. I guess sports science focuses on athletes, Is there much average Joe science? apart from weight loss. I'm amazed also at how easy walking is, and how little calories I burn walking - which is why I started - to lose a few pounds.