I've dealt with lumbar back pain for a few years on and off, I think the lumbar region is the most common area of the back for pain.
the lumbar region is sometimes referred to as the lower spine
Yes that is correct, and the middle back is usually called the thoracic region, while the neck area is called the cervical region.
 A lumbar strain is a stretch injury to the ligaments, tendons, and/or muscles of the low back. 
I've definitely had lumbar strains before, as many Americans have I think, almost nine out of ten adults have back pain at some point in their life.
The stretching incident results in microscopic tears of varying degrees in these tissues
Back pain
Back pain is pain felt in the back. The back is divided into neck pain (cervical), middle back pain (thoracic), lower back pain (lumbar) or coccydynia (tailbone or sacral pain) based on the segment affected. The lumbar area is the most common area affected. Episodes of back pain may be acute, sub-acute, or chronic depending on the duration. The pain may be characterized as a dull ache, shooting or piercing pain, or a burning sensation. Discomfort
, the lumbar and cervical types are more common than the rarer thoracic stenosis. Although stenosis can be found isolated in one region of the spine, developmental spinal stenosis will most likely involve both the cervical and lumbar sections.
The age that people develop spinal stenosis is correlated with change in the joint’s biomechanics. Because of this, there has been a recent increasing trend seen by physicians, of lumbar spinal stenosis is being more commonly diagnosed in older patients. Low back pain accounts for 17% of all physician visits of