Back pack vacuum cleaners are a popular choice for office buildings. With many floors to clean, the speed of cleaning is greatly improved with the use of a back pack. It is a common misconception that they hurt your back after a while.
If they are hurting your back, you need to look at if you are wearing the machine correctly. The weight of the vacuum should be dispersed around your hips with the pressure being on the waist strap. Try a little experiment, by putting the back pack on and sliding the shoulder straps off. If the vacuum falls to the ground, it means the waist strap is not doing its job. This is because you are not wearing the machine correctly.
Ensure the waist belt is tight but comfortable, it is in good condition and located just on top of the hips. The shoulder straps are there just to balance the machine. The shoulder strap should not be the load bearing part of the machine. when you put the machine on for the first time, loosen the straps completely, then put it on your back. Tighten the straps, but at the same time put your right hand over your heart. Tighten the strap so that you can slide your hand in and out like putting your shoes on. Not too easy and not to hard, but just right. you have now ensured that you are wearing the machine correctly.