This concept is simple to understand when you understand that muscles do not have a mind of their own. Muscles tighten and relax as a response. There are two primary ways that a tight muscle becomes tight.
Way #1: The person uses their pecs a lot more than the muscles on the back of their shoulders. When someone uses a muscle a lot, then it gets stronger, even when it’s relaxed. This creates an imbalance in how strong the pecs are at rest, and they eventually pull the shoulders forward. This doesn’t mean that this person has to be doing a lot of pushups or bench press. In fact, unless someone works out their back muscles, most of our life is spent with our arms out in front of us, so developing this imbalance is as easy as sitting at a desk all day long.
Way #2: The person has a weak rotator cuff and scapular stabilizers. Many people who do exercise, neglect to train the rotator cuff muscles and the muscles that keep the shoulder blade firmly glued to your back. It’s not their fault. Most of our life we’re chained to desks, at least throughout school, and for many people for work. So we gradually adopt lazier forms of movement, taking the path of least resistance. Eventually stabilizing muscles weaken. When the body feels this weakness it calls in other muscles to attempt to stabilize. The body does not know that calling in the pec minor may result in worse movement patterns and potential injury, it just wants to feel stable and accomplish the task at hand.
Now that we understand what causes someone to get a tight pec minor, let’s move on to how to fix it. For your convenience we have also put together a 3 exercise PDF for you. It’s that green one you can download at the top of the page.