I'm 32 (33 in about 10 days), have chronic back pain, and have been taking Tramadol and Ibuprofen 3 times a day every day for the past 2 years and there is no end in sight. While I do not have pain in my arms, I do get twinges in my back after standing in the same spot for so long. I have to sit down, squat down or lean on the bench for a bit before I can get back to it.
My best advice is to find a range with a stool you can sit on and a rest to put your pistol on so that you are not keeping it suspended in the air the whole time you shoot.
Also talk to your Doctor and see if they have any advice. Also, keep your bloodwork current. Long term Ibuprofen is not really good for you. I'll probably need a new liver and/or kidneys in the next 20 years or so if I keep having to take it.
Brain (Use this one the most)