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The joints are protected by the ligaments that hold them together.
The spine is no different. A joint's second line of defense are the muscles that
help hold it stable. When these muscles become weak, the ligaments can get
overworked and sore.
A good example of how muscles can protect joints is that when a 150
pound man jumps from a height of three feet, his femur sustains a force of 450
foot/pounds. However, we know that it only takes 400 foot/pounds of force to break
the biggest bone in the leg! We don't fracture this bone because the quadriceps
muscle protects the bone and joint by absorbing the impact.
In the spine, the muscles that protect and guard the joints also have to
shelter the nerves and spinal cord from harm. This is a big, important job, as
injury to these structures can mean lots of problems. They do that job by holding
the bones in-line as you do things like bending and lifting. They actually contract
to support the spine before you make a move! For example, when you move your
arm your spine muscles must contract so that your spine doesn't collapse. What happens when these muscles don't contract in
time or are too weak to hold the bones in line? Muscular instability. This can
cause pain in the associated joints, nerve irritation, and painful surface muscles.
Based on the research, this is this single biggest cause of low back pain.
There are two muscles that protect the spine on a day to day basis: deep multifidus and transversus abdominus. The
multifidus muscles
are small muscles close in to the spine that atrophy in a first episode of back pain.
These muscles are deep in your low back and stomach. You can't readily
feel them from the skin.
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