It’s not stretching but I’ve had sudden onset back pain several times since taking up cycling years ago. Stretching and massage targeting the areas helps reduce the occurrence but the only thing that was gotten it to go away completely is regular visits to my chiropractor (who’s also a cyclist).
I’ll say I don’t buy into the whole chiro philosophy that they can fix everything by adjusting you, but I have had tremendous improvements in reducing the tight muscles in my back and neck which has lead to no longer “throwing out” my back.
N of 1 and all that.