Inspired from Why does it hurt the next day after doing significant exercise? with its excellent answer:
In climbing, you can put tremendous load on the hand/fore-arm muscles (specifically, flexor pollicus longus and flexor digitorum profundus). What happens is often that you are not just fatigued, but that the muscles seem to "lock up" - they subjectively feel "hard", it seems impossible to relax and the problem does not go away after a few minutes, by stretching (which will actually become quite painful) or by self-massage.
The muscles are not necessarily showing the burning sensation that indicates lactate buildup according to the answer for the linked question. This effect seems to be a main cause for athletes to prematurely end a training session because there's little hope to solve it except for a long (hours...) rest. People have trouble opening doors etc. because the muscles seem to be completely wasted. Onset is immediate during or after a straining exercise, not later, like DOMS would be. After a good nights sleep, the problem usually seems to go away, it is not a day-long soreness.
Is that effect rather related to damage (micro tears etc.) or some chemical process? Is there a good way to prevent it, either in the short or long term, i.e. by training specifically for/against it? Are you aware of other muscles that show the same behaviour? I have only experienced it in those.