If you’re anything like me, we’ve got short arms like a T-Rex, so that means using stems longer than 60mm makes my back hurt.
For the most part, bikes come stock with a minimum of 90mm stems. I usually recommend swapping out the stem before anything else on a bike. Not only does this help out your bike, but it also allows for better control. One of my favorite stems would be the Dirty Dog Reaper. This stem is only 50mm long and great on your back because you won’t be leaning so far forward.
Then again there might be other factors why your back might hurt such as proper bike fit, medical history and etc. But changing out the stem might be the quickest and possibly cheapest way to find out if it helps.