Use to be worse for me when I did 6-7 hours a backpack work a day. But since no one seems to know how do deal with bulk removal I jump into that and let my guys try to do the finish product with the back packs. Are they as good as I am on them hehehehe not even close but using a leaf plow and a self propelled fradan 18 hp blower is a lot more fun then a br 600 all day.
But iv managed to injure both shoulders at one time or another from backpacking and that's like game over for that season. I tripped once on a pool cover cable and landed on my back with a backpack on and it popped my left shoulder out and every so often it acts up from clean ups now so I do my best to do a variety of tasks to keep the repetition down.