The pressure was both external and internal. It was external in that something was pressing down on them. It was internal in that their bodies had suddenly and inexplicably become heavy.
Thor began to ventilate heavily because of the pressure. Arthur encouraged him, "It only feels so bad now that we are experiencing it for the first time. The pressure should lessen when we get used to it."
Thor gritted his teeth and said, "I hope you're right."
Arthur looked up to the top of the mountain and said, "I hope I'm right too."
What he said was indeed the case. They got used to the pressure after a while.
They only got used to it, though. The difficulty of climbing the mountain didn't reduce one bit. They had only acclimated themselves to the unnatural pressure. It was still difficult for them to stand and very difficult for them to walk.
