What Happens When You Stretch

Relate & Review:
As we learned previously through our notes and a video, muscles are comprised of segments called sarcomeres. These can contract and elongate according to whether the muscle is relaxed or engaged. When we stretch, our sarcomeres elongate until each one is fully stretched and the muscle fiber is completely relaxed, then collagen fibers in connective tissue "pick up the slack" and pull in the same direction as the stretch. The main nerve endings in muscles are proprioceptors (mechanoreceptors). Like Mr. Orre said, these tell your where you are in space. Basically, if you close your eyes and lift your arm, the proprioceptors tell you how high your arm is raised. They are present in all nerve endings of joints, muscles, and tendons. Muscle spindles are the most prevalent proprioceptors in the muscles. The muscle spindle stretches when a muscle is stretched and triggers an action called the stretch reflex, which contracts the previously stretched muscle. However, this reflex can be reduced through prolonged and frequent stretching. This article mentions dancers as some of the few humans that possess very little to no stretch reflex, as they stretch like crazy.
Quotes:
"While this type of control provides the opportunity for the greatest gains in flexibility, it also provides the greatest risk of injury if used improperly." (2)
- This quote was interesting to me as it shows the potential risks for pushing your body to the max in order to reduce your stretch reflex. I think this shows the lengths dancers are willing to go to in order to further their careers. It is sad that so much is expected of people so that they can stand out and be better.
"Just as the total strength of a contracting muscle is a result of the number of fibers contracting, the total length of a stretched muscle is a result of the number of fibers stretched -- the more fibers stretched, the more length developed by the muscle for a given stretch." (1)
- Strength and flexibility are inversely related based on sarcomere length. This unit is still blowing my mind as I never even knew sarcomeres existed beforehad, I just thought the muscle as a unit would move like pulling taffy at a candy shop. Now it makes more logical sense. 
"Another reason for holding a stretch for a prolonged period of time is to allow this lengthening reaction to occur, thus helping the stretched muscles to relax. It is easier to stretch, or lengthen, a muscle when it is not trying to contract." (3)
- I have witnessed this firsthand! It's the coolest phenomonon. I remember sitting in the splits hating life as I couldn't get all the way down, and I was clenching all my muscles, then all of a sudden, my hamstrings just relaxed and it was way easier.