In reply to Slackboot:
I don’t think this is exclusive to boulderers. Years ago I was having a chat with a very famous climber from back in the day (who did mainly trad but some bouldering too). Each of his fingers was the size of a mini banana, like you might find in a kids lunch box.
I asked him if his fingers got tired and his skin hurt, like mine did and he said ‘no, they don’t hurt at all’. I didn’t ask what they were like when not climbing.
A decade or so later, my fingers are ‘thicker’ than they used to be. They are stiff and don’t bend through the same range that they used to. The joints used to swell and hurt, especially after long bouldering sessions, and especially climbing indoors. But in recent years, I’ve been consistent with the finger care and that has not been an issue.
From what I’ve read, all of the climbing and finger training stiffens the fingers. This makes them stronger but reduces mobility.
I do wonder, if I stopped climbing, would they change back to how they were?