I have discovered that issues with the right hand position holding up the clarinet can deteriorate over time, causing serious problems if not corrected.
Such a problem occurred with me. When I reached out to turn a page with my right hand, I always felt a shocking pain shoot up through my forearm. I just ignored the symptom, which usually flared up during professional rehearsals and concerts, when I had little time to reflect on the cause.
Now that I am practicing more at home, I had to face the problem. I played around with it over several sessions. (I've noticed I use that phrase a lot, "played around with". It reminds me of Diane Ackerman's wonderful book, "Deep Play", a lush and poetic exploration of the subject from a Darwinian point of view. Ultimately, play is how we best learn.)
It wasn't until I was out for a walk one day that I noticed now my right hand never let go of the clarinet. I had tension continuously in that forearm. The epiphany was more physical than spiritual, but I suddenly felt my hand's natural openness, each finger's distance from the others, inhabiting its own muscular "space".
It brought new meaning to my habitual suggestion to students to shake out their hands to find their natural poise. I've also told them their hands should feel like they are holding a large sponge ball. Now my hand felt joyously like it was holding a large ball, not quite basket ball size, but just big enough to call each digit out from the center of my hand into a poised fan shape.
I carried this openness into my next practice session, and found that my thumb collapsed from this ideal position under the weight of the clarinet.
I "played around" with that habitual issue, exaggerating the "openness" of my hand way beyond the position required by the keys. The muscles of my forearm were not weak at all, just lazy.
So I invented a little exercise, clarinet pushups, to remind my hand of its inherent openness. For those who wish to try this exercise, here it is.
While standing, hold the clarinet way out in front of your body, so your arms are extended. Level the instrument so the mouthpiece is slightly below the plane where your mouth is. Without bringing it to your lips, push up and toward your mouth with your thumb to bring the instrument up to your playing position, while keeping your arms extended. Repeat this "pushup" a dozen times or so.
Do not forget to mind your general stance, meaning your overall tension and balance. It's useless to isolate the thumb while torturing other muscles. You should feel a little burn in the front of your right shoulder. The weight of the clarinet is not the sole responsibility of your thumb, or your shoulder, but is, with good "use", transfered to your back where the real strength lies.
Don't worry that your fingers and hand extend beyond the keys while doing this. Focus on the space between the fingers during this exercise, not the position of the hand.
Now, with your arms extended and open, as if you are about to give someone a hug, use your thumb and arms, in that order, to bring the instrument to your mouth to play. Never lose awareness of both hand's openness.
Play a C scale two octaves, not worrying if you over shoot a few keys. Again, the point is to contract that open fan shape as little as possible.
If you, like many woodwind players, have suffered from discomfort in your right hand from holding the instrument, this exercise will help you become aware of, and perhaps resolve, those issues.
My right hand hand facility has improved, and I rarely have shocks up my arms when turning pages.