What Happen's When You Stretch

Relate and Review:

As we've learned in our notes before, muscle fibers are made of myofibrils, which are in turn constructed of multiple sarcomeres. Each sarcomere has over lapping parts with one another. When a muscle contracts, the area that overlaps increases, essentially shortening the muscle. The reading talks about the counter of that, which is when the muscle is being stretched, muscle fibers are pulled to its full length and disorganized fibers are realigned. Proprioreceptors in the muscle (the primary ones being the stretch receptors) relay messages to the nervous system that triggers the stretch reflex, which is the muscles initial resistance to stretching. However, If you hold a stretch long enough, the proprioreceptors will start to decrease its signaling, which allows the muscles to slowly lengthen. Another cause for relaxation is when tension due to contraction exceeds a certain threshold and causes a lengthening reaction. A lengthening reaction is when a muscle is inhibited from contracting, therefore forcing a relaxation. In the muscle unit, we learned about how often muscles are paired together so that when one contracts, the other has to relax (ie. biceps and triceps). This is called reciprocal inhibition--when the bicep contracts, the triceps are inhibited from contracting.

Quotes:

• "This realignment [when you stretch] is what rehabilitates scarred tissue back to health" (1). So then if you get a large cut, is it important to stretch it to prevent or reduce scarring? I think people would be interested to learn about how to not scar.
• "The muscle spindle contains two different types of fibers which are sensitive to change in muscle length and the rate of change in muscle length" (2). It never ceases to amaze me how cells can record such minute things. The rate in which a muscle is lengthening? That's amazing. 
• "In [a sit up] the back muscles also contract [in addition to the stomach muscles]" (3). That's pretty counter intuitive and a little hard to picture, but it really shows how the body is way more complex than an average person will ever know. Learning about how muscles cooperate could really make exercising more efficient.