UKC

I've been indoor climbing and bouldering for a couple of years now, averaging maybe 5 times a month, sometimes more, sometimes with a month without climbing at all. In that time period I've almost never had pumped forearms.

However, the past few weeks, starting on the traversal wall for warm-up as usual, a couple of the lowest level routes has seen my arms get completely pumped and I have real trouble gripping anything for the session. This is such an abrupt change, I'm struggling to understand it and, most importantly, find a solution. As it is now, an hour after climbing, my forearms are still tight as if I'd been struggling up the most challenging climb, yet I did very little and nothing beyond comfortable for my level.

Anyone know what's going on?

This is almost certainly what’s called “flash pump” from your warm-up traverse just being too intense/long.

Basically, you need to warm-up more slowly on easier terrain before you tackle these traverses or step off before the end when you feel a hint of pump coming on. Once you are up to temperature you’ll be able to clear pump and can start to allow yourself to get progressively slightly more pumped.

Not wishing to alarm you but it sounds a bit like Compartment Syndrome. The ususal disclaimers about unqualified internet diagnosis apply!

You would need to give us a lot more info: what chnges have there been in your lifestyle, diet etc; Are there other symptoms of strength loss in other activities. Have you changed jobs, suffered stress etc ... ?

I agree it's the most likely cause, given the limited info we have to go on. A contributory factor may be that it's got colder lately so he may be starting from a colder state and not realising that his body needs to be warmer before he's able to cope with even relatively modest forearm workload without getting pumped.

You might have got into a habit of gripping too hard on the holds without realising it. Sometimes it can be possible to grip less and still not come off.

As others have said it could be "flash pump" - warming up on something a bit too hard. You've implied these were pretty easy warmups though. A simple thing to try would be to use a massage ball on your forearms, I had a problem with getting irrationally pumped last year and a friend pointed out how tight my forearm muscles were. I've taken to using a massage ball regularly and it's made a world of difference to my stamina.

Don't suppose you've recently started supplementing creatine? This can lead to the effect described in some climbers.

You're getting older. 

Definitely this. Amputation above the shoulder is the only answer