What happens when you stretch?

Relate and Review:

I remember learning in class that a sarcomere is a section of a myofibril where protein fibers overlap and slide past each other during the contraction and relaxation of muscles. I thought it was interesting how the reading outlined how the muscle fiber is pulled out fully one sarcomere at a time, then the connective tissue picks up the slack. When I was recovering from scarred tissue, I remember a nurse explaining parts of this process to me. The article also confirmed that it is this realignment that helps tissues recover from scarring, as it helps realign the disorganized strips of muscle fiber by pushing it in the direction of the tension.

1. "Proprioceptors are the source of all proprioception: the perception of one's own body position and movement": I thought this was an interesting line because of how sensitive the proprioceptors actually are. Any change of tension or basic movement is detected and they reside in so many places. For example, proprioceptors are found in the nerve endings, muscles, tendons, and fibers. 
2. "When stretching, it is easier to stretch a muscle that is relaxed than to stretch a muscle that is contracting": By allowing the antagonists to relax, you can get a better stretch. In track, we learned that you can stretch out your hamstrings better by keeping your leg erect. This makes sense because keeping the muscle relaxed can provide a deeper stretch. 
3. "Some sources suggest that with extensive training, the stretch reflex of certain muscles can be controlled so that there is little or no reflex contraction in response to a sudden stretch": This is a very interesting concept because one would consider reflexes to be uncontrollable. However, for professional athletes, muscular control can actually be achieved.