Well a sprain is irrelevant to the conversation, as that deals with ligaments and not muscles. They said it was a "moderate strain". I've only taken a few 200 level anatomy and physiology classes so I'm no where near qualified enough to assess exactly what the means. From my knowledge, however, a strain is typically when muscle fibers are torn. It can also refer to just an overstretching/overworking of the muslce. So saying its a moderate strain, to me, means that he probably partially tore the muslce, meaning that he tore some of the muscle fibers. If you could find something about the difference between calling something a strained muscle as opposed to a torn muscle, that would be helpful. A pulled muscle is called a muscle strain. (Here’s a little known fact: a wrenched ligament is always called a sprain, whereas a torn muscle is always called a strain.) Although there may be other factors that make you vulnerable, the immediate cause of every muscle strain is traumatic stretching and tearing of the tissue, often due to the force of your own muscular contraction. The more the muscle is torn, the worse the strain from that I gather they are the same thing. I am pretty confused though :) After doing some reading, it seems like first degree and second degree strains are partial torn muscles, where as a third degree is a complete tear of the muscle. Also, a first degree muscle strain is usually just refered to as a pulled muscle. So a moderate strain is a partial tear. Thats what I am starting to get as well.