That's why I got the Zipper. It can be a little bit of a learning curve, managing your hoses so that you keep both hands on the Zipper but for large commercial, it's a shoulder saver.Got use the rotary or the Zipper more. Slinging that wand back and forth for years on end it what's wearing your shoulder out.
Just show the doctor the motion and how many hours a day you do it. Times a week, a month, a year, a decade.