he is 10 weeks old! small little hikes to build his body. Lots of treats and small snacks throughpout the hike till they get older (just like a kid). By the time he is 6 months he will be able to do several miles and gain. By 10 months -1 yr he will do two trips to your one by running up and back to check on you. I have had 3 awesome hiking dogs I started as puppies. All awesome and could go anywhere by 1 yr of age. One was a shepard cross, the next one was an Akita, the last one was the best a Australian cattle dog/blue healer named Tazz
. I miss my pups.
BTW don't carry the pup. He is a big dog. If you carry them all over too much as a pup they want the same and as BIG pup...:-O. Golden retrievers are not pocket dogs. I have seen folks carry their large breed pups all over when young and then the pup turns into a dog and wont hike well or won't get too far without whining or laying down on the trail and refusing to go (usually due to being over weight). Small hikes and fun is what he needs to build confidence and strength to start. Let him tell you when he is done. He will tell you.
First thing to remember is don't allow him to get fat! Folks feed their dogs way too much and then they have difficulty hiking.
the most important is to watch the pads of the feet . In snow/ice they can get cut up bad. Same if on rock all day long.
Oh and altitude does not affect dogs the same way as us. They adjust easier and quicker. Don't know why.
Have fun with your new pooch.