My med large dogs (80lbs) are lazy couch dwellers. I have taken them herding from time to time, I sometime rollerblade with the one who enjoys it, and I do walk them both 4-5 miles every day - but they don't really seem to need much yard room - my yard is a little bigger than normal and they do like to race back and forth when another dog walks past - but other than that they come back in to sleep on my bed. The smaller dogs I have known (especially terriers) are a lot more active than my guys.