I notice that most of the time, after a tough match, when I go home, my back feels OK. However, after I sleep and wake-up the next morning, I have pain. I can barely bend forward as I feel my back is a bit "locked". It takes a few hours for the muscles to warm-up and I regain some flexibility. About me, I'm 27, I workout 3 times a week and play tennis 1-2 times on the weekend, i'm in pretty good shape and have been for years. I stretch every other day, trying to target my hamstrings as I know they are a cause of lower back problems. I suffered a herniated disc (L5) last July, however I don't think it's an issue anymore.I don't understand, during the week i'm fine when I workout, it's really the morning following a tennis match. Could the kick serve be the culprit? Is there anything I can do to avoid this?