Based on the OP's other thread, mal = Malinois not Malamute.12-18months, though being a working malamute I'd say she could handle it at 12. Just go slow and build her muscle and cardiovascular system the way you would yours, not too fast because you could overwork her heart or pull muscles etc
Malamutes and Malinois are both working breeds so I'd say 12-18 months would be fine in either case. I've never gotten my dogs X-rayd for running or biking purposes, however it'd be interesting to know the benefits. Not sure I'd want to put my dog under GA unless it was completely necessary.Based on the OP's other thread, mal = Malinois not Malamute.
They probably grow up a little faster.