Lazy Aussie?

Question
Actually, I have two questions. We adopted a one year old Aussie from the pound almost a year ago. He was poorly socialized and very skittish. With lots of work, he is coming out of his shell more every day, although still overly protective of his home. My daughter has been home from college for 2 months now, and he still barks and growls at her when she enters the house. She plays with him, takes him for walks and feeds him occasionally. What else can we do to help him accept her as "one of the pack"?

My other question is whether there is such a thing as a "lazy" Aussie. We take him to the dog park to run almost every day, and he wears out after about 20 minutes, trotting beside me and panting like a locomotive. On hikes, he lags behind after about the first mile and will even stop and lay down! He sleeps the rest of the time. The vet has checked him over carefully and can find nothing wrong (no heart issues, thank goodness), and said he's just a "couch potato". He's not overweight, and eats a premium dog food.  I worry that I'm pushing him too hard on hikes, but he really wants to go along. I've heard that Aussies bred for show can be less active. He has an amazing coat and looks like a show dog. Could this be the case, or is he just lazy?

Answer
The show types do tend to be heavier boned, and heavier coated, and less active than the real working stockdog types (I know, I own one of those LOL - couch potato she is NOT).  She also still growls or barks at my boyfriend's older sons who were not around for her puppy hood, unless they call her the way I do.  I would have your daughter use the dog's name in the same way, same tone, and speak to the dog before entering the home, and come in bearing treats periodically.  Unfortunately, these dogs don't generally accept things that they were not socialized to as pups, so he may always be a bit leery of her since she isn't a constant presence in the home.  What you want is a signal that alerts him that it is indeed her, and not an intruder.  FWIW, dogs often run out of steam playing with other dogs, or catching frisbees, and Aussies are smart enough to conserve energy when they need to.  Hiking is tough on dogs that don't have toughened pads, too, so if you are on rough terrain, hot asphalt, or other icky substrate, the dog may decide he's had enough.
Sleeping a lot could be a sign of general anxiety - the dog gets tired being on "high alert" all the time.  
This site has lots of stock dog photos:
http://www.pinciecreek.com/
And this would be more reflective of the show type:
http://www.paradoxaustralianshepherds.com/