yeah me too, until recently. You're taller than me so maybe not as strenuous. Took me a while to figure out what was causing it. If I use the wand on stairs now, I start to feel it right away, so I force myself not to be lazy and go to the truck for the stair tool. I was doing the same thing, powerwashing a recovery tank that I am going to install in my new truck. I had the lance high up in the air, trying to get under some of the baffles. When I was done, my shoulder was aching fiercely. Some times, we never learn.