For the first couple of weeks (maybe a bit longer) with the Zipper, I do recall having some pain occasionally between my upper shoulder blades....
But, I think in my case it was a bit of my posture and getting used to the tool....
Also, I attributed it to a group of muscles that just had not been used much since the old days of drag wands I grew up on.
But now, I really don't notice any pain or aches at all from the Zipper..
For speed even with dry passes, we almost double our cleaning times. We have been using the Zippers since the middle of Sept 2014, and really a lot....
I watch some videos (even including mine) of when we first started using the Zipper (we were needing work), and I see how much more efficient we have become with hose management, squaring off rooms with furniture to clean, figuring out what is the best time saving steps in a room.
On a couple thick cut pile....oh yeah....they can be ridiculous to move the Zipper without adjusting them...but we usually just plow through and get er done!
I would love to see some videos of how people with these concerns are using the Zipper to maybe help....
So far, anyone who has come and visited and used the Zipper with me, has not had difficulty....BUT, I come from and education back ground and maybe I am getting lucky trying to give tips to those people right away while they are with us and have a good experience....
Hoping you all find the magic like we did