Anatomy Question

So I have read a lot on this forum that you can't make muscles longer...just bigger or smaller.  That makes sense.  So my question is: what is flexibility?

I am a former dancer.  I can do the splits, I can rest my chest flat against my thighs, heck I can even kick my own head from behind.  What allows me do this but other people can"t.  If my muscles aren't longer, what makes them more bendy than someone who cant touch their toes.  In ballet we always talked about stretching as lengthening...if that isnt whats going on, what is?

Here's my understanding: Flexibility is the range of motion of a joint. If your muscles are tight, you won't be able to reach full range of motion of your joint, while if your muscles are loose, you can stretch further.

But the muscles are still attached to your bones in the same place, and aren't any longer.

So what does it mean for a muscle to be tight?  Again I am going back to its either big or small.  Sorry, I just have not take biology since highschool.

Tight = not stretchy? I don't really know.

We need a melkor.

Muscles are attached to bones with ligaments, which are stretchy elastic fibers. Muscles themselve contract (shorten) and return to a ready rest state (tonus) but are ready to contract again when the Action Potentials are activated by the nervous system. You are stretchier then others because you have worked those ligaments and muscles to that point. That is evident in that the first time you tried to do the splits, you probably couldnt get your legs completely straight...but now you can....

Range of motion or flexibility is mostly controlled by the central nervous system. Most people are very flexible when under anesthesia. Muscles contract and that causes limited range of motion. In most cases you have to train your central nervous system to allow (relax) your muscles to increase flexibility.

For muscles, the opposite of "contract" is "elongate".  As mentioned above, many people find it difficult to fully elongate their muscle as muscle tend to remain in a partially contracted state.  Through training you can learn to achieve the fully elongated state which gives you a greater range of motion.  This is often referred to as "lengthening" the muscles but the term is misleading as the muscles are not getting longer, they are elongating.

Original Post by kellymcfarling:

That is evident in that the first time you tried to do the splits, you probably couldnt get your legs completely straight...but now you can....

Unless you're me.  Then you never could get your legs completely straight and likely never will be able to.  I was so inflexible, they kicked me out of gymnastics as a kid.  No matter how much I stretched, it never really helped.  I must have very short ligaments?  Or something?

muscles are attached to the bone with tendons while ligaments are bone to bone

Original Post by kellymcfarling:

Muscles are attached to bones with ligaments, which are stretchy elastic fibers. Muscles themselve contract (shorten) and return to a ready rest state (tonus) but are ready to contract again when the Action Potentials are activated by the nervous system. You are stretchier then others because you have worked those ligaments and muscles to that point. That is evident in that the first time you tried to do the splits, you probably couldnt get your legs completely straight...but now you can....

 muscles are attached to the bone via tendons whereas ligaments attach bone to bone