Chronic injury of muscle in upper back

About 6 times a year I feel a popping sensation in my upper back (during weight-lifting exercises, when swiming, or even house chores) followed by pain and 2-3 days of disability. This chronic injury is very frustrating and I wish there was someway to strengthen the tissue to prevent it from tearing again. I assume the injury is a partially torn muscle, but I suppose it could also be a partially torn tendon instead. But let's go with the muscle possibility since that has a slightly better prognosis...

Below is the text that I wrote one day in November 2010 when I was recovering from my latest injury:

from http://en.academic.ru/pictures/enwiki/83/Semispinalis.png

I think I finally identified the muscle that I keep injuring in my upper back. But there are so many of them, I'm not sure. My latest suspect is the semispinalis muscle that lies either side along the spine underneath the trapezius and rhomboids. I surfed the internet looking for muscles that extend (straighten) the neck which are oriented paralel to the spine and which seem to be in the same location as my injury. There are several, but when I read that the semispinalis muscle also aids in extending the ribs, I felt a little more confident that I've diagnosed at least the site of my injury. You see, I sing bass in my church choir and sometimes when I injure my upper back and neck, I can't sing the low notes as strongly or loudly. This is a strange thing to link up with an injured back muscle, but if the semispinalis does indeed work upon the rib cage then it makes sense that an injury to that muscle would cause some disability in the finely-tuned actions of the ribcage muscles when forcing air out of the lungs during singing. I hope you see the link. I must admit that the website that I found this information on does not seem to be the most reputable. I don't see anything to make me doubt its veracity, but I have a weird feeling about the service that American Academy of Manual Medicine promotes. They also don't use punctuation well on their website!