Good stretch for an achy back?

depends on what part of the back.

I like ear to shoulder stretches.
So, lean your head to the left side and gently pull your head more towards that shoulder. To me, it feels better if you also put your right hand on your right shoulder and gently pull the shoulder down.
Repeat on right side.

If you have a tall chair, sit in it and interlock both hands behind your head. Lean back and feel the stretch.

Also, get a tennis ball (I currently have one sitting on my coffee table to remind me to do this) use it against a wall and roll your back/shoulder area on it. If I'm massaging my right side, I'll hold my left hand up/out so that I can catch the ball when/if it falls, instead of having to pick it up off the ground repeatedly.

My lower back is typically my problem. If you have that going on, i suggest stretching your hamstrings and buttocks. Sounds weird but believe it or not, tight hammys and glutes tend to pull on your lower back muscles and cause lower back pain.

The #2 stretch in the video link below (pidgeon pose) is what i call the "miracle stretch" lol. It seriously rids me of all my lower back pain when i do it regularly.

https://youtu.be/xSuvEdVxcMQ?si=nxtCmGiDvfS2F4vz


And this video shows the hamstring stretches I do in the shower. I let the hot water loosen me up before doing these stretches.

https://youtu.be/LVY692zJK0A?si=fhfk5sValy65x8Ce

Take ibuprofen and get a professional massage.

try a hot water bath or a hot water bottle and maybe a vibrator to your back muscles and some good long sleep session on a good bed...and magnesium supplements too...

what works for me is finding a bar to hang on and just hang there for 20 seconds or so. it seems to get the kinks out.

Shoulder dislocates with a broom handle or band
Maybe do the cat cow flexion movements for back

Free arm hang from a pull up bar

this works for me
[media=https://youtu.be/zechBkcIMf0]