Noticed recently when I tried to pull up the sleeves of my favorite tattered-old-wear-around-the-house shirt, that my right sleeve stopped at the forearm whereas the left zipped right up as normal.

I'm right-handed so I guess that shouldn't be so surprising. What was surprising was the "amount" of the differencee.

BTW - I don't do arm-strengthening excercises - only have time for aerobics.

I'm guessing it all has to do with the mouse, especially since that shoulder is often sore, and we have been incredibly busy at work lately.

Well, that's the first time I've heard that was caused my clicking a mouse. Spanking a monkey, on the other hand...

It is definitely not unusual- when using a hand dynamometer, there is an expectation for the dominant hand to be at least 10#/sq. inch stronger.

And who cannot forget the difference in arm size in Gabriela Sabatini- holy Popeye to Olive Oil!!
(waiting for verbal backlash from Gaga4Gaby)

Trust me PS, the monkey didn't do it...this time. Though I'd rather it had.

Not spazzing on it or anything. No chance I'll look like Nadal...I hope.

Just surprised me that mousing around seemed to be able to cause that on its own.

Weird, I've noticed my left (non-dominant0 arm is bigger than my right. At times, I've considered using higher weights on my right side to try to get them to match up.

I've actually started some upper body strength training again. More because I think it helps keep the arms and torso in shape for maintaining that "ergonomic" posture, and might help prevent the arm and shoulder soreness on my dominant side.

Also the conclusions from this abstract of a Canadian study suggests that something I've thought about doing might be useful: using my left hand now and then for the mouse.

Since all you do is click it's not surprising that most people can learn to use the opposite hand.

Unfortunately office equipment is not always designed or positioned to suit easy switching.