Climbing Mountains too fast can kill you, cause the body is not used to the fast change of oxygen levels, thats why nowadays, people climb tall/huge mountains with oxygen bottles
@Cernunnos
He basically spends all his free time wandering the mountains on foot to gather the herbs. Even back home, he's tending the gardens and doing other stuff requiring moving the body. In fact just using a mortar and pestle can be laborious enough if the matter to be powdered is tough. He might be a doctor in training, but his work seems to be highly physical. If he lived in a city in the same position, he would no doubt me much weaker, though.