Muscle strains are a very common orthopedic injury. A muscle strain AKA a “pulled muscle” happens when a muscle is overstretched or torn. This can occur due to overuse, excessive muscular contraction, fatigue, etc. Muscles that are commonly “pulled” include hamstrings, calves, quads, and low back muscles.
Anatomy of a muscle strain
In order to understand the anatomy of a muscle strain, it is important to understand the structure of muscles. Muscles are large bundles of individual, long, thin muscle fibers - picture the end of a witches broom.
Grade 1: 0-5% of muscle is involved, muscle fibers are overstretched, not torn, focal tenderness and swelling, no loss of function
Grade 2: 5-50% of muscle fibers involved/torn, pain, swelling, bruising
Grade 3: 50-100% of muscle fibers involved, complete rupture of muscle, loss of function of muscle
So should I stretch it?
After straining a muscle, many people immediately feel the need to begin stretching that area. Incidentally, this is the wrong way to help the muscle heal initially. Stretching a strained muscle (or aggressively foam rolling it) further pulls the muscle fibers apart and makes it much harder for them to heal back together.