Lumbar strain (acute, chronic): A lumbar strain is a stretch injury to the ligaments, tendons, and/or muscles of the low back. The stretching incident results in microscopic tears of varying degrees in these tissues. Lumbar strain is considered one of the most common causes of low back pain. The injury can occur because of overuse, improper use, or trauma. Soft-tissue injury is commonly classified as "acute" if it has been present for days to weeks. If the strain lasts longer than three months, it is referred to as "chronic." Lumbar strain most often occurs in people in their 40s, but it can happen at any age. The condition is characterized by localized discomfort in the low back area with onset after an event that mechanically stressed the lumbar tissues. The severity of the injury ranges from mild to severe, depending on the degree of strain and resulting spasm of the muscles of the low back. The diagnosis of lumbar strain is based on the history of injury, the location of the pain, and exclusion of nervous system injury. Usually, X-ray testing is only helpful to exclude bone abnormalities.
Nonsteroidal anti-inflammatory drugs (NSAIDS) relieve pain and inflammation and include OTC formulations (ibuprofen, ketoprofen, and naproxen sodium). Several others, including a type of NSAID called COX-2 inhibitors, are available only by prescription. Long-term use of NSAIDs has been associated with stomach irritation, ulcers, heartburn, diarrhea, fluid retention, and in rare cases, kidney dysfunction and cardiovascular disease. The longer a person uses NSAIDs the more likely they are to develop side effects. Many other drugs cannot be taken at the same time a person is treated with NSAIDs because they alter the way the body processes or eliminates other medications.
Activity: Bed rest should be limited. Individuals should begin stretching exercises and resume normal daily activities as soon as possible, while avoiding movements that aggravate pain. Strong evidence shows that persons who continue their activities without bed rest following onset of low back pain appeared to have better back flexibility than those who rested in bed for a week. Other studies suggest that bed rest alone may make back pain worse and can lead to secondary complications such as depression, decreased muscle tone, and blood clots in the legs.

Pain is generally an unpleasant feeling in response to an event that either damages or can potentially damage the body's tissues. There are four main steps in the process of feeling pain: transduction, transmission, perception, and modulation.[12] The nerve cells that detect pain have cell bodies located in the dorsal root ganglia and fibers that transmit these signals to the spinal cord.[33] The process of pain sensation starts when the pain-causing event triggers the endings of appropriate sensory nerve cells. This type of cell converts the event into an electrical signal by transduction. Several different types of nerve fibers carry out the transmission of the electrical signal from the transducing cell to the posterior horn of spinal cord, from there to the brain stem, and then from the brain stem to the various parts of the brain such as the thalamus and the limbic system. In the brain, the pain signals are processed and given context in the process of pain perception. Through modulation, the brain can modify the sending of further nerve impulses by decreasing or increasing the release of neurotransmitters.[12]

The diagnosis of low back pain involves a review of the history of the illness and underlying medical conditions as well as a physical examination. It is essential that a complete story of the back pain be reviewed including injury history, aggravating and alleviating conditions, associated symptoms (fever, numbness, tingling, incontinence, etc.), as well as the duration and progression of symptoms. Aside from routine abdomen and extremity evaluations, rectal and pelvic examinations may eventually be required as well. Further tests for diagnosis of low back pain can be required including blood and urine tests, plain film X-ray tests, CAT scanning, MRI scanning, bone scanning, and tests of the nerves such as electromyograms (EMG) and nerve conduction velocities (NCV).
Imaging is indicated when there are red flags, ongoing neurological symptoms that do not resolve, or ongoing or worsening pain.[5] In particular, early use of imaging (either MRI or CT) is recommended for suspected cancer, infection, or cauda equina syndrome.[5] MRI is slightly better than CT for identifying disc disease; the two technologies are equally useful for diagnosing spinal stenosis.[5] Only a few physical diagnostic tests are helpful.[5] The straight leg raise test is almost always positive in those with disc herniation.[5] Lumbar provocative discography may be useful to identify a specific disc causing pain in those with chronic high levels of low back pain.[41] Similarly, therapeutic procedures such as nerve blocks can be used to determine a specific source of pain.[5] Some evidence supports the use of facet joint injections, transforminal epidural injections and sacroilliac injections as diagnostic tests.[5] Most other physical tests, such as evaluating for scoliosis, muscle weakness or wasting, and impaired reflexes, are of little use.[5]
4. Just swing it. For the front-to-back hip swing stretch, lie on the left side with hips stacked, propped up on the left elbow. Bend the left leg to a 90-degree angle and raise the right leg to hip level with toes pointed. Keep abs tight and swing the right leg all the way in front, then swing it all the way to the back, squeezing the booty along the way. Switch sides.

When a muscle contracts, it shortens. Take the biceps for example. Without getting too technical, the biceps are attached at the forearm and shoulder. When your biceps contract, they shorten and bring those two points closer together. When you rest, the muscle returns to its normal length, and the two points move farther away. Constantly contracting your biceps over a long period of time would cause them to get shorter, even at rest.
Low back pain that lasts at least one day and limits activity is a common complaint.[7] Globally, about 40% of people have LBP at some point in their lives,[7] with estimates as high as 80% of people in the developed world.[22] Approximately 9 to 12% of people (632 million) have LBP at any given point in time, and nearly one quarter (23.2%) report having it at some point over any one-month period.[7][8] Difficulty most often begins between 20 and 40 years of age.[1] Low back pain is more common among people aged 40–80 years, with the overall number of individuals affected expected to increase as the population ages.[7]
Kidneys — The kidneys are a matched pair. One painful kidney can cause back pain on one side or the other. Kidney pain can feel like back pain, and may occur on only one side. It is usually quite lateral, and just barely low enough to qualify as “low” back pain. However, when kidney stones descend through the ureters, they can cause (terrible) pain in the low back. Kidney stone pain is often so severe and develops so rapidly that it isn’t mistaken for a back pain problem.

Radicular pain. This type of pain can occur if a spinal nerve root becomes impinged or inflamed. Radicular pain may follow a nerve root pattern or dermatome down into the buttock and/or leg. Its specific sensation is sharp, electric, burning-type pain and can be associated with numbness or weakness (sciatica). It is typically felt on only one side of the body.

Since the hip flexors are so easy to overuse and strain, it is important to stretch them before exercise or strenuous activity. Because of their connectedness to other muscle groups in the legs (like the quadriceps), it is important to stretch the muscle group as a whole, not individually. This ensures that the entire area is warmed up and ready for the strain of exercise or activity, not just one or two individual muscles.
Radicular pain. This type of pain can occur if a spinal nerve root becomes impinged or inflamed. Radicular pain may follow a nerve root pattern or dermatome down into the buttock and/or leg. Its specific sensation is sharp, electric, burning-type pain and can be associated with numbness or weakness (sciatica). It is typically felt on only one side of the body.
^ Jump up to: a b c Furlan AD, Yazdi F, Tsertsvadze A, Gross A, Van Tulder M, Santaguida L, Gagnier J, Ammendolia C, Dryden T, Doucette S, Skidmore B, Daniel R, Ostermann T, Tsouros S (2012). "A systematic review and meta-analysis of efficacy, cost-effectiveness, and safety of selected complementary and alternative medicine for neck and low-back pain". Evidence-Based Complementary and Alternative Medicine. 2012: 1–61. doi:10.1155/2012/953139. PMC 3236015. PMID 22203884.
Medications: A wide range of medications are used to treat acute and chronic low back pain. Some are available over the counter (OTC); others require a physician’s prescription. Certain drugs, even those available OTC, may be unsafe during pregnancy, may interact with other medications, cause side effects, or lead to serious adverse effects such as liver damage or gastrointestinal ulcers and bleeding. Consultation with a health care provider is advised before use. The following are the main types of medications used for low back pain:
In this study, one patient with sciatica was sent for ten MRIs, which produced 49 distinct “findings,” 16 of them unique, none of which occurred in all ten reports. On average, each radiologist made about a dozen errors, seeing one or two things that weren’t there and missing about ten things that were. Yikes. Read a more detailed and informal description of this study.
Stop focusing on a specific diagnosis. Up to 85% of low back pain can be classified as "non-specific." This means that the origin of your pain cannot be localized to one specific structure or problem. While common diagnostic tests for low back pain can show the bones, discs, and joints with great detail, no test can tell the exact cause of your pain with 100% accuracy.
Moist heat may help relax your muscles. Put moist heat on the sore area for 10 to 15 minutes at a time before you do warm-up and stretching exercises. Moist heat includes heat patches or moist heating pads that you can buy at most drugstores, a wet washcloth or towel that has been heated in a microwave or the dryer, or a hot shower. Don’t use heat if you have swelling.
Sleeping in an awkward position can cause you to be in pain from the moment you wake up. The best sleeping position for lower back pain may be sleeping on your side with your knees drawn up close to your chest (also known as the fetal position). Placing a pillow or two between your legs, while sleeping on your side, helps to reduce stress on your lower back. Sleeping on a too soft mattress can also cause lower back pain. A firmer mattress is best.

I think you should mention that for some people, stretching is not the solution and that it will deteriorate their posture. Some people need stretching, but most people I know need to strengthen their "overstretched" hip flexors. Many people can't do a single hanging leg raise. Check this site if you want to know more about the importance of hip flexors Report
MRI (or magnetic resonance imaging) scan is a radiology technique which uses magnetism, radio waves, and a computer to produce images of body structures. MRI scanning is painless and does not involve X-ray radiation. Patients with heart pacemakers, metal implants, or metal chips or clips in or around the eyes cannot be scanned with MRI because of the effect of the magnet.
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