Now when you're up here, focus on squeezing your upper back muscles ... Make sure you don't feel any strain in your neck. Five more seconds. All right. We're actually going to stand up straight ...
Source: Focus Medica. A condition characterized by stretching or tearing of a muscle. The strain often occurs in the lower back and in the muscle in the back of the thigh. Occurs when a muscle is ...
The continual strain on your neck, shoulder and upper back muscles causes these muscles to tear (on a microscopic level). Your body tries to prevent this tearing by forcing these muscles to knot up.