There are four common types of back pain: pain that increases with flexion (bending forward), pain that increases with extension (leaning backwards), radiating, shooting, or burning pain, and finally, muscular aches.
Pain that increases with flexion, such as bending forward to touch your toes, is usually the result of a herniated or bulging disc. Flexing the spine pushes disc material to the back of the spine (which is the part of the spine where nearly all herniations occur), exacerbating the pain. Spending long periods of time sitting can also cause further irritation, as it is difficult to not flex the spine while seated.
Back pain that increases with extension is usually the result of irritated facet joints. Each vertebra is part of four facet joints, two connecting with the vertebra above and two connecting with the vertebra below. These joints are very sensitive to pressure, and extending the spine by leaning backwards increases compression in these joints. In addition to facet joint injury, there are also a variety of conditions which could contribute to extension-based back pain, such as osteoarthritis and spondylothesis (a type of dislocated vertebra).
Pain that radiates and “shoots” down the leg that may be accompanied by a burning sensation is generally referred to as sciatica. The term sciatica simply refers to the type of pain rather than any one specific underlying condition. In other words, sciatica is caused by sciatic nerve irritation and many different things can irritate this nerve. Sciatica could be caused by a tight piriformis muscle (which can pinch the nerve) or could be caused by a herniated disc pressing on one of nerve roots that contribute to the sciatic nerve. Both of these injuries can result in the same symptoms.
The last major type of back pain is aching muscles. This type of pain is not felt in the spine itself but rather on either side of the spinal cord in the muscles known as the erector spinae. In this type of pain, there is a feeling of tightness which has two predominate causes: an over-worked muscle or a muscle that is splinting an injured area.
An over-worked erector spinae is generally the result of poor posture or poor lifting form. Poor posture and lifting form can result in tight muscles because these two things interfere with the way the muscle is built to contract. The fix here is to make sure you maintain the natural “S” shape of the spine whenever lifting an object or sitting for extended periods of time.
The other major reason for erector spinae tightness is when these muscles attempt to “splint” the low back. Just like a broken bone is splinted, the brain forces the erector spinae to maintain a tight contraction in order to prevent the lower back from moving. This is the result of the brain trying to prevent further injury or can be the residual effect of a previous lower back injury. This generally requires some sort of exercise program to correct.