That was your crash course in muscles.

Muscles are the larger, fleshier part, red in the diagram. They are responsible for actual movement; this is where the impulse receptors are that lead to the firing and contraction. Muscles can change size, grow and shrink, become stronger or weaker. Tendons attach the muscles to the bones, and are not capable of changes in size. You are born with either shorter or longer tendons, which contributes to your ability to put on muscles mass. If your tendons are taking up the majority of the space, you will not be able to build as big of muscles. If your muscles are taking up most of the space, they have a lot of room to be able to grow. Tendons are 2% elastin, so they have some stretch. They kind of work like a spring during powerful movements. Ligaments are not stretchy at all and you don't want to mess with those guys.

I chose to write about this today because I have some mild tendonitis behind my knee at the moment. Tendonitis is inflammation of the tendon, and is caused by overuse. There isn't much you can do it for it, except give it the standard RICE (rest, ice, compression, and elevation), and be more careful with your training to help prevent recurrence. Generally, tendonitis is a problem for people who do the same activities over and over. Two of the times I've gotten it were from too much of the same activity too quickly, and with bad form.

You have to listen to your body and know your weaknesses. For me, I've got some foot problems, so I have to be really careful about running distances. My feet place extra strain on my leg muscles, so making the same motion over and over in bad form is going to give me problems. I also need to make sure I warm up my muscles properly if they're going to endure more strain than expected. Each person is different, so tune in to your body, say good morning, and see how you two can work this out.

I also think there's an interesting metaphor here: tendonitis results from doing the same thing too many times, or many times with bad form. I think you would see a similar pattern in communication and human conditions. Just sayin'.

Photo belongs to A.D.A.M Medical Encylopedia