As you know, videos are an excellent tool for learning. I made one to help visualize some traits of a muscle injury. Before looking at the video, a brief discussion should be done fist.
The technical term for a muscle injury is called a strain. More specifically it is divided into grades I, II and III. Grade III is when the muscle is completely separated into two parts. Grade II is when the muscle is still intact but, partially torn. Grade I is the most common type and is characterized by having portions of the muscle torn, yet fully intact. In other words, in grade 1 injuries, various types of x-ray or MRI studies do not show rips or tears in the muscle. The injury occurs to small, deeper portions of the muscle and are not easily seen in studies. However, all three grades produce inflammation, swelling and pain.
Some of the common or instinctive things an injured person will do is to stretch and put ice (hopefully!) on the area. Ice is always a good treatment to decrease the swelling and pressure created by inflammation. Stretching is the point where further injury can occur.
As the muscle swells, there are pressure nerve endings which are stimulated that give a feeling of stiffness to the muscle. So, the instinctive thing to do is to stretch the muscle to help lessen the tightness and hopefully make it feel better. Though it can help decrease the pain and tightness, it is typically very temporary and might help for a few minutes. The problem is that there is a high chance it will lead to further tearing of the muscle.
The reason is that the stretch is way too aggressive, even though it might not be painful when stretching. Instead, a very slight awareness of a stretch should be sensed. This awareness is typically much less than when the muscle is not injured. It’s very easy to over do it. You have to be careful and have a lot of patience.
Take a look at The Tissue Test video to drive home this point.