Recently I have had two incidents where I ended up with spasms and lasting inflammation in my back. The first time it happened I wasn't doing a full workout, just messing around with pullups at home. I stopped doing the pullups and was hanging out. I reached down for something low on the floor and ::twing:: by back started hurting. I went to the doctor the following day and she said that my muscles were spasming and knotted like a charley horse. the perscription was muscle relaxers and Aleve. It was gone by the next week. About 3-4 weeks later, I was doing DB Swings and pullups. My back was fine until the following day. At first I thought it was just DOMS, but the pain got worse. This time I used the leftover muscle relaxers and Aleve. That was Monday, and I'm about 98% better now. The pain isn't crippling, but it makes it difficult to bend more than about 10* forward. I can stretch and do it, but the muscles are very tight and sore. My wife massaged my back and said that the muscles in the affected area were swollen and more prominent than my other back muscles. Any advice on preventing this? I don't want it to become a repetitive occurance.
The spasms are just above the curve of my lower back, near the area highlighted in red in this picture.