No problem to put on an empty backpack. Try connecting the backpack to longer trips, not just a walk around the block.

For pulling pulks, you may start with empty pulks at the age of 1. They are too playful before that, but then you may begin to introduce some tasks to them.

When starting to use the pulk, make sure you are on an empty field. Trees will make a mess and may discourage them. It will take some time before they understand the principle. Never use just a rope between the dog and a pulk, unless it is a pulk with a brake. (Eskimo type) Use fixed poles, then it will be OK. Be patient, for there will be a lot of stops and harness tangle and so on.

But personally I would not let them do any pulling until the age of 1,5. That is because of the harness fitting. The dogs are growing until the age of two, not so much in length and height, but in chest and mucles. The harness we use here is the web type, and it must fit quite good, otherwise it will chafe. Both too big or too small will make the harness chafe. Always check for this in the beginning. The pictures from my trip gives you an idea of the harness.

Another activity is just a rope from the harness to a person. Do NOT use an elastic band at the start. We call it rope-pulling (snøre-kjøring) and it will be very fun if you have kids that are old enough to walk/run with the dog. Here also start on an open treeless field!

Elastic ropes are not much used here. If it is used, the elastic part is very short (2 feet). It is very tiring for the dog if there is a long elastic rope. The pull never stops, and this may wear them out.