Anyone who spends even a couple hours a day on a computer can suffer from RSI (Repetitive Strain Injury) -- and jugglers certainly fall in a high risk category as well. If you use a computer at all, you'd do well to peruse the Typing Injury FAQ and the UN-L R.S.I. Page. Jugglers should also read over the page by Steven Ragatz on warming up.
First-hand advice from the net follows.
If the following is a frequently asked question, I apologize in advance. I have been experiencing pain in my right wrist (on the side down from my little finger). I suspect it may be juggling induced, may be from club passing too much. On the other hand (bad pun vaguely intended), I usually only club pass once a week which isn't very much at all. So maybe it's not juggling related.... I am right-handed so maybe years of over-using that hand are catching up with me. Do other people have problems with their wrists? What can you do to alleviate it? Strengthen your wrists? I am going to the doctor on Thursday (19th) night. So if anyone has time before then, I'd be interested to hear what problems other jugglers have had.
Two things that I have done to alleviate wrist and hand pain are aerobic exercise and stretching exercises. You can check out any number of books at the library on stretching, however, if you are dealing with an injury, you should probably ask your doctor or physical therapist what types of exercises she would recommend. I also took up XC-skiing several years ago when I first noticed my wrist problems, I also jog and bike. I would say that this has done more for alleviating my wrist and hand pain than anything else.
As with anything else, and especially with regard to things medical, YMMV. The key, of course, is to check with your doctor or PT before undertaking any exercises lest they exacerbate your injury.
There are a number of resources on the net that you can check, ftp to ftp.csua.berkeley.edu, and in the directory ~/pub/typing-injury you will find a wealth of information on various wrist and hand injuries (although, understandably, these articles discuss injuries related to typing, you can cull quite a bit of information that might be helpful for a juggling-related wrist or hand injury). On Usenet, you can check out sci.med.occupational which discusses wrist injuries quite a bit or check out some of the mailing lists. One, in particular, sorehand, is dedicated to the discussion of wrist and hand injuries. You can subscribe to sorehand by sending mail to listserv@vm.ucsf.edu, the message body should read 'subscribe sorehand Your Name'
In any case, good luck, keep us posted on your progress.
I've had some problems with tendonitis and carpal tunnel syndrome due to typing, so I'm always interested in this topic... I'm curious about something Mark Olson just posted, however:
I do some wrist and forearm stretching each morning and before as part of my juggling warm-up, but why does aerobic exercise help? Does better and stronger circulation combat problems like these?