Please, only use a backpack vacuum if you are young and have no back problems! Same for those wonderful but heavy Orecks.
Our work is part physical labor and part mental labor. If you dont take good care with your equipment, over time your back will suffer. I am speaking as both an RN AND a house cleaner. Nurses often have back trouble, because we do a lift of lifting patients, bending over, etc. I am quite sure a professional cleaner will face the same issues. This is yet another reason I use my Shark wand vacuums. They are super light and easy to lift and they are super good on normal house dirt, dust, pet fur, etc.