Here's an ergonomic tip to immediately improve your posture and alleviate nagging back pain.
We are taught from an early age that wallets go in your back pocket. That's a bad, bad thing. It's almost as if the clothing designers are in cahoots with the wallet manufacturers to make sure that's where they go. The only problem is that a wallet in your back pocket hurts your posture and can cause back, neck, and shoulder pain.
Standing up the back pocket is a fine place to stow your wallet. But when you sit down you start an avalanche of body mechanic problems. When one cheek is higher than the other you end up twisting the pelvis. This is bad enough but it doesn't stop there. The spine becomes misaligned. Then your shoulders slump. And you really start to hurt after that.
The healthiest option is to move that wallet to your front pocket. If you must keep your wallet in your back pocket you should remove it before you sit down. Maybe even get one of those snazzy wallets with the chain so you don't forget it. You should also keep your wallet as thin as possible. Even when it is in your front pocket a smaller wallet will be a benefit.