There over stretching can occur when the movement or action focusing more on the insertion point or joint rather then the belly of the muscle (i.e. straight leg versus bent leg hamstring stretches). When we are taking about the lumbar, decompression or lengthening through the use of pelvic anchoring and muscular breath work is much more effective then stretching. Also, lengthening of the lumbar spine in conjunction with the rest of the posterior chain will lengthen AND stabilize.
During acute strain or injury stretching can further irritate and prolong healing cycle.
Myofacial release is a very important part of maintaining proper muscular length and effectiveness.
I HIGHLY recommend you look at www.foundationtraining.com. Their program focuses on effective length of musculature and joints combined with proper effective tension of muscle and joints. Not just flexibility. There is also a lot of emphasis on lumbar stability and decompression. It has changed the life of clients and myself.
Hope this helps,