Muscle flexibility, in very simple terms, is the length of motion that a muscle or muscle group can achieve from its shortest length to its longest.
You may have poor muscle flexibility. In this case the muscle or muscle group is unable to either contract to its minimum or extend to its maximum length or a combination of the two.
A muscle may be able to contract to its maximum amount and not be able to fully extend to its maximum length. Or it can fully extend but may be unable to fully contract.
Your body is a very efficient organism. Muscles will not continue to either fully contract or extend if not forced to over a regular period of time. If you fail to fully extend your muscles, thereby taking them to their maximum length, over time you will lose the ability to do so.
Generally speaking, throughout your life your muscles will naturally want to go into a contracted state unless there is some injury or disease that disrupts the normal nerve impulses needed to maintain tone. This can be seen with the paraplegic or quadriplegic where the spinal cord has been severed.
With a brain injury, as in cerebral palsy, you will witness the opposite where the muscle's nerves loose their "governing" mechanism and fail to impede the body's inherent desire to become spastic.
These neurological diseases or injuries cause involuntary actions that are out of your control.
However, in a normal nervous system, in the absence of disease or injury, this contraction and lengthening of your muscles is voluntary.
So, if you fail to exercise your muscles on a regular basis by forcing
maximum contraction and maximum lengthening you will eventually allow
that muscle to lose the ability to do so.
You see this all the time with those that are bedridden, have a fractured arm held in a bent plaster cast for weeks, and the elderly who fail to engage in regular daily activities that promotes and encourages full muscle range
Once this loss of muscle flexibility is established it becomes very difficult to regain. It is possible but it takes regular daily effort.
Your goal is to maintain or build strength, endurance and flexibility throughout your life or you will eventually suffer the consequences of failing to do so.
Muscle flexibility exercises take little time and minimal effort but regularity is essential.