This is a really interesting thread.
My first response would be, "Get in better shape." I think that's still a good answer, but after reading this, I can see why that isn't a great answer for many. I'm still going to plug it for a moment though - I'm managing two herniated disks and some impaired nerve function from a third. Staying in shape is extremely important to me. I'm trying to make it to 50 before I have surgery. At the end of the day, pushing myself to exercise is way cheaper and way less damaging that corrective surgery will be. Even a light exercise regimen should help.
Ibuprofen before brewing is also a good call. Taking an anti-inflammatory before exercise is proven to reduce inflammation better than taking it after inflammation begins.
Beyond that, I do things in stages. It's more for time savings on brew days, but I crush my grain at least a day before the brew and I move my fermenter to the basement the day after the brew. It helps.
The two hardest items I have to tackle are moving the 5 gallon containers of water up the stairs on brew day and then taking the fermenter downstairs when chilling is complete. The latter is the absolute worst. Carrying an uneven, bulky load down a narrow flight of stairs is really hard, and it puts a lot of strain on my disks. If anyone has a good suggestion for that, I am all ears.
Edit: To chill, I just pour the hot wort into the fermenter and then leave the fermenter outside overnight in even reasonably cool weather. It works fine. I haven't had any change in beer quality or in rate of infection. I literally just have to walk the bucket to the front porch. It's quick, easy, and then I toss in yeast and move the fermenter to the basement the next morning. In the summer I have to work a little harder, but for 9 months out of the year, chilling is very low effort.