hmmm, saw this come up in my 'recent forum posts list' and yeah, backpain can be a problem if you spend much time driving a lift during the day. But i saw the date this was originally posted and thought, sure why not, new commentary isn't a waste of time if it helps people right?
Well my.02 worth i guess ;o)
Look at reducing the amount of shock your body receives while driving the machine would be the key goal i suppose.
There are 4 things to consider,
1- the type of tires you have on the lift, since the shockwaves from impacts travel through the lift you would want a good cushion tire, not too hard, not too soft. Definitely NOT a poly tire, they are very hard and do not reduce the shock from impacts at all. A good rubber tire like a non-marking type would have the best effect but you would also have to deal with wear issues as the softer tire would wear out faster but given your goal is to aid in reducing operator wear and tear that's a small price to pay compared to the medical costs to the operator and downtime that leads to reduced productivity.
2- the seat you use on your lift, a good suspension seat is also key to reducing shock to the operator while driving a lift. If you have a good seat that has good cushioning in the padding and also a mechanism in the seat suspension that will also reduce shock to the operator. Sure good suspension seats are expensive but the cost ratio of production, operator health costs is a no brainer.
Buy the good seat and he will be happier, healthier and will work and produce more in the long run ;o)
3- now this might seem a bit picky and most people don't think about it much but every guy usually keeps a wallet in their back pocket, that causes you to sit with your lower spine in an awkward position slightly. You might not think so but it does, that is not normal positioning for your spine so i can over extended periods of time cause pain in your spine that radiates outwards and can get to be extreme if you don't remedy that problem by just taking your wallet out of your pocket. I had a therapist tell me that once and i thought to myself, they were crazy, i've had a wallet in my back pocket for years and never had problems before. But low and behold, when i took it out while i was sitting, a lot of that pain went away when i started sitting properly without anything in my back pockets.
4- use a back brace. If you have issues with your back, using a back brace will help hold your spine straight and take the stress away from the muscles. They can help a lot. Most doctors will give you one anyway if your being treated for back pain and alignment issues so why not right?
But all in all i think the things mentioned will make a world of difference.

Not to mention some exercising can help tone your muscles and strengthen them to help keep your spine straight. Now i know not everyone can do this because of chronic problems but if you can, do it ;o)

Hope everyone has had a great holiday and hope your new year is as well, stay safe and healthy everyone ;o)