People who make motorcycles must hage Go-rilla arms. I have noticed the trend in auto's also of late.
I'll agree that it sounds like you are reaching for the bars/have poor riding posture. It is hard to say with the info given and would be difficult over the interweb to know for sure anyway. Do you get a cramp (feels like a knife twisting) between your spine and shoulder blade? If so you either need to move forward or pull tha bars back, my choice was to go forward and it was a good move on my part since I was getting a seat anyway. Slide up in the seat for a ride and see if it helps. You'll know about the reach then. Get a backrest, it will help solve a lot of problems once you get it adjusted correctly.
One other thing. Ride more and if you don't have one, get a windshield. Sounds kinda corney, but we use muscle groups for rideing that aren't normally used in life. How many activities do you have that require your arms being outreached for long periods, even when resting on the bars. Get a throttle lock or use the cruise, stop death gripping the grips, sit up straight (yes your mom was right), stay hydrated when riding. Even short rides in warmish weather can start you to dehydration. Ever get thirsty? You are behind the curve if you do.
Just things to start with. Your arms should be flexed to a comfortable angle and not at full reach. I see folks ride like that and wonder how the can turn. It is demanding and requre repositioning the body to manouver. Riding is still an activity so treat it as such. Chaces are you'll get more out of it.
Cheers