Tendons

Tendon injuries... well... suffice to say they are the opposite of fun. So, what is the root cause? Ok... brief A&P lesson - tendons are composed of collagen bundles (allows them to stretch) and ground substance (provides structural support). Collagen is arranged in a hierarchical fashion (the figure explains it a lot better than anything I could write). The ground substance, which is comprised mainly of proteoglycancs, basically serves as a glue.
Now, being that collagen is what allows the tendon to stretch, one would think that the properties of the fibrils (i.e., the lowest level) are what causes the problem. Not so... it is the "stuff" holding them together (this is by far my favorite quote of the article). To summarize their findings, when the fibrils were tested in isolation, they could stretch to 100% of their original length. However, a tendon can only stretch 10-20% before breaking. Ergo, "stuff" is the problem! They don't really give any suggestions for how to go about preventing injuries, but presumably research into such topics will now be better focused. #20

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